http://bugs.winehq.org/show_bug.cgi?id=31914
--- Comment #3 from Henri Verbeet hverbeet@gmail.com 2012-10-08 08:31:17 CDT --- (In reply to comment #2)
If it's not a WINE bug, why has it worked before 1.5.10?
Probably because something changed in the way Wine renders things, and glc can't handle the new situation very well. The main change like that between 1.5.9 and 1.5.10 was changing the AlwaysOffscreen default, but there have been changes to e.g. winex11.drv around that time as well. If you want to narrow down the specific commit that broke it, do a bisect between 1.5.9 and 1.5.10.