http://bugs.winehq.org/show_bug.cgi?id=21072
--- Comment #7 from Dan Kegel dank@kegel.com 2009-12-19 21:12:26 --- Yeah, WINEDEBUG settings can accidentally make bugs go away (which qualifies them as Heisenbugs :-).
If you see err:heap messages, it typically means you've hit either a wine bug or an app bug, and the next step may be to apply the heap checking patches, do winetricks heapcheck, and see if you get any interesting heap warnings. And the next step after that is to also run the app under valgrind... but that's hard, since it makes the app run Really Slow and take Lots Of Ram, and only pinpoints a bug occasionally. (But when it does, it's really the bomb.)