I'm still having problems with debugger highlighting even in a 3.6 image upgraded to 5387. The best way I can come up with to give you a repeatable way to see this:
1. Start with a 5387 image like the one at ftp://st.cs.uiuc.edu/pub/Smalltalk/Squeak/3.6beta/Squeak3.6b-5387.zip
2. Go into the preferences and enable browseWithPrettyPrint
3. Open the Package Loader (SqueakMap).
4. File in Celeste Removal. This results in a UndefinedObject methodsFor:? debugger prompt.
5. Browse the stack.
Guess I'll file the Celeste Removal issue seperately. ;)
Ken