I am seeing the following very annoying error in 50511 spur. Open a Playground, type [ (both open en close are inserted, with the cursor in-between), type : (to start a block arg), boom: RBParseErrorNode(Object)>>doesNotUnderstand: #isInstance OCASTClosureAnalyzer>>changeVariableClass: OCASTClosureAnalyzer>>visitArgumentNode: [ :each | self visitArgumentNode: each ] in OCASTClosureAnalyzer(RBProgramNodeVisitor)>>visitArgumentNodes: OrderedCollection>>do: OCASTClosureAnalyzer(RBProgramNodeVisitor)>>visitArgumentNodes: OCASTClosureAnalyzer>>visitBlockNode: RBBlockNode>>acceptVisitor: OCASTClosureAnalyzer(RBProgramNodeVisitor)>>visitNode: [ :each | self visitNode: each ] in OCASTClosureAnalyzer(RBProgramNodeVisitor)>>visitSequenceNode: OrderedCollection>>do: OCASTClosureAnalyzer(RBProgramNodeVisitor)>>visitSequenceNode: RBSequenceNode>>acceptVisitor: OCASTClosureAnalyzer(RBProgramNodeVisitor)>>visitNode: OCASTClosureAnalyzer>>visitMethodNode: RBMethodNode>>acceptVisitor: OCASTClosureAnalyzer(RBProgramNodeVisitor)>>visitNode: OCASTSemanticAnalyzer>>analyze: RBMethodNode>>doSemanticAnalysis RBBlockNode(RBProgramNode)>>doSemanticAnalysis RubSHTextStylerST80(SHRBTextStyler)>>privateStyle: [ self privateStyle: text. view ifNotNil: [ view stylerStyledInBackground: text ] ] in [ backgroundProcess := [ self privateStyle: text. view ifNotNil: [ view stylerStyledInBackground: text ] ] forkAt: Processor userBackgroundPriority ] in RubSHTextStylerST80(SHTextStyler)>>styleInBackgroundProcess: [ self value. Processor terminateActive ] in BlockClosure>>newProcess Has this already been reported ? It makes the image almost unusable... Sven