This happens when the popup of OCompletion is open and you do something else then accepting OCompletion. The popup is there, alive, and after a short timeout it should be closed. But when trying to do so....20 debuggers appear in my image.

ECMenuMorph >> handleMouseEnter: anEvent
�� self activeHand newKeyboardFocus: controller editor morph.
�� anEvent wasHandled: true.

it seems "controller editor" is answering nil. This is the stack:

13 June 2011 12:27:25 pm

VM: Mac OS - intel - 1067 - Croquet Closure Cog VM [CoInterpreter VMMaker.oscog-eem.56] Croquet Cog 3.0.0
Image: Pharo1.3a [Latest update: #13257]

UndefinedObject(Object)>>doesNotUnderstand: #morph
�� Receiver: nil
�� Arguments and temporary variables:
�� aMessage: �� morph
�� exception: �� MessageNotUnderstood: receiver of "morph" is nil
�� resumeValue: �� nil
�� Receiver's instance variables:
nil

OMenuMorph(ECMenuMorph)>>handleMouseEnter:
�� Receiver: an OMenuMorph(869793792)
�� Arguments and temporary variables:
�� anEvent: �� [324@500 273@512 mouseEnter 48058628 nil]
�� Receiver's instance variables:
�� bounds: �� 109@502 corner: 309@518
�� owner: �� nil
�� submorphs: �� #()
�� fullBounds: �� 109@502 corner: 309@518
�� color: �� (TranslucentColor r: 0.9 g: 0.9 b: 0.9 alpha: 0.016)
�� extension: �� a MorphExtension (873725952) [eventHandler = an EventHandler; mouseD...etc...
�� borderWidth: �� 1
�� borderColor: �� (TranslucentColor r: 0.5 g: 0.5 b: 0.5 alpha: 0.016)
�� selected: �� 1
�� firstVisible: �� 1
�� titleStringMorph: �� nil
�� controller: �� an OController
�� context: �� an OContext
�� pageHeight: �� 4
�� itemHeight: �� 16
�� detailMorph: �� nil
�� detailPosition: �� 309@502
�� lastActivity: �� 48055845

MouseMoveEvent(MouseEvent)>>sentTo:
�� Receiver: [324@500 273@512 mouseEnter 48058628 nil]
�� Arguments and temporary variables:
�� anObject: �� an OMenuMorph(869793792)
�� Receiver's instance variables:
�� timeStamp: �� 48058628
�� source: �� a HandMorph(843055104)
�� windowIndex: �� nil
�� type: �� #mouseEnter
�� buttons: �� 0
�� position: �� 273@512
�� handler: �� nil
�� wasHandled: �� false
�� startPoint: �� 324@500
�� trail: �� {(290@508). (273@512)}

MouseMoveEvent>>sentTo:
�� Receiver: [324@500 273@512 mouseEnter 48058628 nil]
�� Arguments and temporary variables:
�� anObject: �� an OMenuMorph(869793792)
�� Receiver's instance variables:
�� timeStamp: �� 48058628
�� source: �� a HandMorph(843055104)
�� windowIndex: �� nil
�� type: �� #mouseEnter
�� buttons: �� 0
�� position: �� 273@512
�� handler: �� nil
�� wasHandled: �� false
�� startPoint: �� 324@500
�� trail: �� {(290@508). (273@512)}

OMenuMorph(Morph)>>handleEvent:
�� Receiver: an OMenuMorph(869793792)
�� Arguments and temporary variables:
�� anEvent: �� [324@500 273@512 mouseEnter 48058628 nil]
�� Receiver's instance variables:
�� bounds: �� 109@502 corner: 309@518
�� owner: �� nil
�� submorphs: �� #()
�� fullBounds: �� 109@502 corner: 309@518
�� color: �� (TranslucentColor r: 0.9 g: 0.9 b: 0.9 alpha: 0.016)
�� extension: �� a MorphExtension (873725952) [eventHandler = an EventHandler; mouseD...etc...
�� borderWidth: �� 1
�� borderColor: �� (TranslucentColor r: 0.5 g: 0.5 b: 0.5 alpha: 0.016)
�� selected: �� 1
�� firstVisible: �� 1
�� titleStringMorph: �� nil
�� controller: �� an OController
�� context: �� an OContext
�� pageHeight: �� 4
�� itemHeight: �� 16
�� detailMorph: �� nil
�� detailPosition: �� 309@502
�� lastActivity: �� 48055845

MouseOverHandler>>transform:from:andSendTo:
�� Receiver: a MouseOverHandler
�� Arguments and temporary variables:
�� anEvent: �� [324@500 273@512 mouseEnter 48058628 nil]
�� originalEvent: �� [324@500 273@512 mouseMove 48058628 nil]
�� aMorph: �� an OMenuMorph(869793792)
�� transformedEvent: �� [324@500 273@512 mouseEnter 48058628 nil]
�� Receiver's instance variables:
�� mouseOverMorphs: �� an Array(a ToggleMenuItemMorph(639369216)'Copy to clipboard' a...etc...
�� enteredMorphs: �� a WriteStream #()
�� overMorphs: �� a WriteStream #()
�� leftMorphs: �� an OrderedCollection()

[self
�� transform: evt
�� from: anEvent
�� andSendTo: aLeftMorph] in MouseOverHandler>>inform:to:originatedFrom:ifNotFocusedDo:
�� Receiver: a MouseOverHandler
�� Arguments and temporary variables:
�� evt: �� [324@500 273@512 mouseEnter 48058628 nil]
�� aLeftMorph: �� an OMenuMorph(869793792)
�� anEvent: �� [324@500 273@512 mouseMove 48058628 nil]
�� Receiver's instance variables:
�� mouseOverMorphs: �� an Array(a ToggleMenuItemMorph(639369216)'Copy to clipboard' a...etc...
�� enteredMorphs: �� a WriteStream #()
�� overMorphs: �� a WriteStream #()
�� leftMorphs: �� an OrderedCollection()

True>>ifTrue:ifFalse:
�� Receiver: true
�� Arguments and temporary variables:
�� trueAlternativeBlock: �� [self
�� transform: evt
�� from: anEvent
�� andSendTo: aLeft...etc...
�� falseAlternativeBlock: �� []
�� Receiver's instance variables:
true

MouseOverHandler>>inform:to:originatedFrom:ifNotFocusedDo:
�� Receiver: a MouseOverHandler
�� Arguments and temporary variables:
�� evt: �� [324@500 273@512 mouseEnter 48058628 nil]
�� aLeftMorph: �� an OMenuMorph(869793792)
�� anEvent: �� [324@500 273@512 mouseMove 48058628 nil]
�� aBlock: �� []
�� Receiver's instance variables:
�� mouseOverMorphs: �� an Array(a ToggleMenuItemMorph(639369216)'Copy to clipboard' a...etc...
�� enteredMorphs: �� a WriteStream #()
�� overMorphs: �� a WriteStream #()
�� leftMorphs: �� an OrderedCollection()

[:anEnteredMorph | self
�� inform: asMouseEnterEvent
�� to: anEnteredMorph
�� originatedFrom: anEvent
�� ifNotFocusedDo: []] in MouseOverHandler>>handleAsMouseEnter:
�� Receiver: a MouseOverHandler
�� Arguments and temporary variables:
�� anEvent: �� an OMenuMorph(869793792)
�� asMouseEnterEvent: �� [324@500 273@512 mouseMove 48058628 nil]
�� anEnteredMorph: �� [324@500 273@512 mouseEnter 48058628 nil]
�� Receiver's instance variables:
�� mouseOverMorphs: �� an Array(a ToggleMenuItemMorph(639369216)'Copy to clipboard' a...etc...
�� enteredMorphs: �� a WriteStream #()
�� overMorphs: �� a WriteStream #()
�� leftMorphs: �� an OrderedCollection()

Array(SequenceableCollection)>>reverseDo:
�� Receiver: an Array(an OMenuMorph(869793792))
�� Arguments and temporary variables:
�� aBlock: �� [:anEnteredMorph | self
�� inform: asMouseEnterEvent
�� to: anEnteredMorp...etc...
�� index: �� 1
�� Receiver's instance variables:
an Array(an OMenuMorph(869793792))

MouseOverHandler>>handleAsMouseEnter:
�� Receiver: a MouseOverHandler
�� Arguments and temporary variables:
�� anEvent: �� [324@500 273@512 mouseMove 48058628 nil]
�� asMouseEnterEvent: �� [324@500 273@512 mouseEnter 48058628 nil]
�� Receiver's instance variables:
�� mouseOverMorphs: �� an Array(a ToggleMenuItemMorph(639369216)'Copy to clipboard' a...etc...
�� enteredMorphs: �� a WriteStream #()
�� overMorphs: �� a WriteStream #()
�� leftMorphs: �� an OrderedCollection()

MouseOverHandler>>processMouseOver:
�� Receiver: a MouseOverHandler
�� Arguments and temporary variables:
�� anEvent: �� [324@500 273@512 mouseMove 48058628 nil]
�� Receiver's instance variables:
�� mouseOverMorphs: �� an Array(a ToggleMenuItemMorph(639369216)'Copy to clipboard' a...etc...
�� enteredMorphs: �� a WriteStream #()
�� overMorphs: �� a WriteStream #()
�� leftMorphs: �� an OrderedCollection()

HandMorph>>handleEvent:
�� Receiver: a HandMorph(843055104)
�� Arguments and temporary variables:
�� anEvent: �� [324@500 273@512 mouseMove 48058628 nil]
�� evt: �� [324@500 273@512 mouseMove 48058628 nil]
�� ofs: �� nil
�� Receiver's instance variables:
�� bounds: �� 447@539 corner: 463@555
�� owner: �� a PasteUpMorph(425197568) [world]
�� submorphs: �� #()
�� fullBounds: �� 447@539 corner: 463@555
�� color: �� Color blue
�� extension: �� a MorphExtension (141295616) [eventHandler = an EventHandler]
�� mouseFocus: �� nil
�� keyboardFocus: �� nil
�� eventListeners: �� nil
�� mouseListeners: �� nil
�� keyboardListeners: �� nil
�� mouseClickState: �� nil
�� mouseOverHandler: �� a MouseOverHandler
�� lastMouseEvent: �� [447@539 mouseUp 48325024 nil]
�� targetOffset: �� 72@4
�� damageRecorder: �� a DamageRecorder
�� cacheCanvas: �� nil
�� cachedCanvasHasHoles: �� true
�� temporaryCursor: �� nil
�� temporaryCursorOffset: �� nil
�� hardwareCursor: �� nil
�� hasChanged: �� true
�� savedPatch: �� nil
�� userInitials: �� ''
�� lastEventBuffer: �� #(1 48325024 447 539 0 0 1 1)
�� lastKeyScanCode: �� 126
�� combinedChar: �� nil

HandMorph>>processEvents
�� Receiver: a HandMorph(843055104)
�� Arguments and temporary variables:
�� evt: �� [324@500 273@512 mouseMove 48058628 nil]
�� evtBuf: �� #(1 48058628 290 508 0 0 0 1)
�� type: �� 1
�� hadAny: �� false
�� Receiver's instance variables:
�� bounds: �� 447@539 corner: 463@555
�� owner: �� a PasteUpMorph(425197568) [world]
�� submorphs: �� #()
�� fullBounds: �� 447@539 corner: 463@555
�� color: �� Color blue
�� extension: �� a MorphExtension (141295616) [eventHandler = an EventHandler]
�� mouseFocus: �� nil
�� keyboardFocus: �� nil
�� eventListeners: �� nil
�� mouseListeners: �� nil
�� keyboardListeners: �� nil
�� mouseClickState: �� nil
�� mouseOverHandler: �� a MouseOverHandler
�� lastMouseEvent: �� [447@539 mouseUp 48325024 nil]
�� targetOffset: �� 72@4
�� damageRecorder: �� a DamageRecorder
�� cacheCanvas: �� nil
�� cachedCanvasHasHoles: �� true
�� temporaryCursor: �� nil
�� temporaryCursorOffset: �� nil
�� hardwareCursor: �� nil
�� hasChanged: �� true
�� savedPatch: �� nil
�� userInitials: �� ''
�� lastEventBuffer: �� #(1 48325024 447 539 0 0 1 1)
�� lastKeyScanCode: �� 126
�� combinedChar: �� nil

[:h |
ActiveHand := h.
�� h processEvents.
�� ActiveHand := nil] in WorldState>>doOneCycleNowFor:
�� Receiver: a WorldState
�� Arguments and temporary variables:
�� h: �� a HandMorph(843055104)
�� Receiver's instance variables:
�� hands: �� an Array(a HandMorph(843055104))
�� viewBox: �� 0@0 corner: 1397@877
�� canvas: �� a FormCanvas on: DisplayScreen(1397x877x32)
�� damageRecorder: �� a DamageRecorder
�� stepList: �� a Heap(StepMessage(#stepAt: -> a PreDebugWindow(851705856))(a PreDebu...etc...
�� lastStepTime: �� 48325012
�� lastStepMessage: �� nil
�� lastCycleTime: �� 48325032
�� alarms: �� a Heap()
�� lastAlarmTime: �� 48325012
�� menuBuilder: �� a PragmaMenuBuilder

Array(SequenceableCollection)>>do:
�� Receiver: an Array(a HandMorph(843055104))
�� Arguments and temporary variables:
�� aBlock: �� [:h |
ActiveHand := h.
�� h processEvents.
�� ActiveHand := nil]
�� index: �� 1
�� indexLimiT: �� 1
�� Receiver's instance variables:
an Array(a HandMorph(843055104))

WorldState>>handsDo:
�� Receiver: a WorldState
�� Arguments and temporary variables:
�� aBlock: �� [:h |
ActiveHand := h.
�� h processEvents.
�� ActiveHand := nil]
�� Receiver's instance variables:
�� hands: �� an Array(a HandMorph(843055104))
�� viewBox: �� 0@0 corner: 1397@877
�� canvas: �� a FormCanvas on: DisplayScreen(1397x877x32)
�� damageRecorder: �� a DamageRecorder
�� stepList: �� a Heap(StepMessage(#stepAt: -> a PreDebugWindow(851705856))(a PreDebu...etc...
�� lastStepTime: �� 48325012
�� lastStepMessage: �� nil
�� lastCycleTime: �� 48325032
�� alarms: �� a Heap()
�� lastAlarmTime: �� 48325012
�� menuBuilder: �� a PragmaMenuBuilder

WorldState>>doOneCycleNowFor:
�� Receiver: a WorldState
�� Arguments and temporary variables:
�� aWorld: �� a PasteUpMorph(425197568) [world]
�� Receiver's instance variables:
�� hands: �� an Array(a HandMorph(843055104))
�� viewBox: �� 0@0 corner: 1397@877
�� canvas: �� a FormCanvas on: DisplayScreen(1397x877x32)
�� damageRecorder: �� a DamageRecorder
�� stepList: �� a Heap(StepMessage(#stepAt: -> a PreDebugWindow(851705856))(a PreDebu...etc...
�� lastStepTime: �� 48325012
�� lastStepMessage: �� nil
�� lastCycleTime: �� 48325032
�� alarms: �� a Heap()
�� lastAlarmTime: �� 48325012
�� menuBuilder: �� a PragmaMenuBuilder

WorldState>>doOneCycleFor:
�� Receiver: a WorldState
�� Arguments and temporary variables:
�� aWorld: �� a PasteUpMorph(425197568) [world]
�� Receiver's instance variables:
�� hands: �� an Array(a HandMorph(843055104))
�� viewBox: �� 0@0 corner: 1397@877
�� canvas: �� a FormCanvas on: DisplayScreen(1397x877x32)
�� damageRecorder: �� a DamageRecorder
�� stepList: �� a Heap(StepMessage(#stepAt: -> a PreDebugWindow(851705856))(a PreDebu...etc...
�� lastStepTime: �� 48325012
�� lastStepMessage: �� nil
�� lastCycleTime: �� 48325032
�� alarms: �� a Heap()
�� lastAlarmTime: �� 48325012
�� menuBuilder: �� a PragmaMenuBuilder

PasteUpMorph>>doOneCycle
�� Receiver: a PasteUpMorph(425197568) [world]
�� Arguments and temporary variables:

�� Receiver's instance variables:
�� bounds: �� 0@0 corner: 1397@877
�� owner: �� nil
�� submorphs: �� an Array(a TaskbarMorph(984088576) a SystemWindow(17563648) a System...etc...
�� fullBounds: �� nil
�� color: �� (Color r: 0.97 g: 0.98 b: 1.0)
�� extension: �� a MorphExtension (666632192) [eventHandler = an EventHandler]� [othe...etc...
�� borderWidth: �� 0
�� borderColor: �� (Color r: 0.03 g: 0.02 b: 0.0)
�� backgroundMorph: �� nil
�� worldState: �� a WorldState
�� griddingOn: �� nil

[[World doOneCycle.
�� Processor yield.
�� false] whileFalse.
�� nil] in Project class>>spawnNewProcess
�� Receiver: Project
�� Arguments and temporary variables:

�� Receiver's instance variables:
�� superclass: �� Model
�� methodDict: �� a MethodDictionary(#beep->(Project>>#beep "a CompiledMethod(6052904...etc...
�� format: �� 132
�� instanceVariables: �� nil
�� organization: �� ('*sound' beep)
('*ma object serialization' maTransientVariables ...etc...
�� subclasses: �� nil
�� name: �� #Project
�� classPool: �� a Dictionary(#UIProcess->a Process in nil )
�� sharedPools: �� nil
�� environment: �� a SystemDictionary(lots of globals)
�� category: �� #'System-Support'
�� traitComposition: �� {}
�� localSelectors: �� nil

[self value.
�� Processor terminateActive] in BlockClosure>>newProcess
�� Receiver: [[World doOneCycle.
�� Processor yield.
�� false] whileFalse.
�� nil]
�� Arguments and temporary variables:

�� Receiver's instance variables:
�� outerContext: �� Project class>>spawnNewProcess
�� startpc: �� 57
�� numArgs: �� 0

--- The full stack ---
UndefinedObject(Object)>>doesNotUnderstand: #morph
OMenuMorph(ECMenuMorph)>>handleMouseEnter:
MouseMoveEvent(MouseEvent)>>sentTo:
MouseMoveEvent>>sentTo:
OMenuMorph(Morph)>>handleEvent:
MouseOverHandler>>transform:from:andSendTo:
[self
�� transform: evt
�� from: anEvent
�� andSendTo: aLeftMorph] in MouseOverHandler>>inform:to:originatedFrom:ifNotFocusedDo:
True>>ifTrue:ifFalse:
MouseOverHandler>>inform:to:originatedFrom:ifNotFocusedDo:
[:anEnteredMorph | self
�� inform: asMouseEnterEvent
�� to: anEnteredMorph
�� originatedFrom: anEvent
�� ifNotFocusedDo: []] in MouseOverHandler>>handleAsMouseEnter:
Array(SequenceableCollection)>>reverseDo:
MouseOverHandler>>handleAsMouseEnter:
MouseOverHandler>>processMouseOver:
HandMorph>>handleEvent:
HandMorph>>processEvents
[:h |
ActiveHand := h.
�� h processEvents.
�� ActiveHand := nil] in WorldState>>doOneCycleNowFor:
Array(SequenceableCollection)>>do:
WorldState>>handsDo:
WorldState>>doOneCycleNowFor:
WorldState>>doOneCycleFor:
PasteUpMorph>>doOneCycle
[[World doOneCycle.
�� Processor yield.
�� false] whileFalse.
�� nil] in Project class>>spawnNewProcess
[self value.
�� Processor terminateActive] in BlockClosure>>newProcess

--
Mariano
http://marianopeck.wordpress.com