Okay, I've been able to reproduce the spurious bug that Igor was seeing ('aContext not in process chain' error). It seems to be related to the fact that the OTDebugger uses an OBFixedButtonPanel and the buttons are not getting updated correctly (or at all), so the buttons are operating on stale contexts. The menu items for the debugger appear to work okay - although the short cut keys may not work - I'll look into this one:). You'll hit the 'aContext not in process chain' as soon as you step out of the original method context. The problem was introduced with pharo0.1-10243dev09.02.3 (pharo0.1-10236dev09.02.2 doesn't have the sticky button problem). I also have fixes for the extra junk on the stack (for create method and for halts/errors), but until the OBFixedButtonPanel issue gets fixed you might want to revert to the non-ob debugger. Dale