Okay, thanks for the info!
The "?? ()"'s belong to the parserthreads trying to parse the project. The reason for the multiple ??()'s in the same backtrace are because the events get called recursively. This is normal (altho "not correct" and IMO it should be changed, yes I know, I'm a purist, grrrr).
Anyway, I assume that the currently active tab is the class browser, right?
The key point here is ClassBrowser::Update(). Something inside that method is allowing null references (hint for debugging: The topmost recognizeable function is the one causing the trouble). And due to the recursive event handling problem^H^H^H^H^H^H^H issue, it's possible that Update() doesn't check for null pointers somewhere. This needs more investigation, and possibly, a couple of sanity_check()'s around. Still I wonder why this only happens with wx2.6... maybe a new event? (ponders)
Anyway try disabling the codecompletion plugin and see what other crashes you can backtrace.
Thanks for your help!