http://bugs.winehq.org/show_bug.cgi?id=25404
--- Comment #3 from Andrew Nguyen arethusa26@gmail.com 2010-12-27 07:08:00 CST --- I sent a patch series, with the last patch providing the actual fix:
http://source.winehq.org/patches/data/69760
The patch set seems to make an XCB assertion fail more frequently, although it was happening before my changes.