http://bugs.winehq.org/show_bug.cgi?id=32058
--- Comment #11 from Alexandre Julliard julliard@winehq.org 2012-11-26 10:25:25 CST --- The previous version was wrong, that's why it was changed.
It worked probably because it resulted in a simpler region. It sounds like your window manager/compositor has trouble with a complex window region. You could try to disable compositing or use a different compositor.