http://bugs.winehq.org/show_bug.cgi?id=20807
--- Comment #4 from Roderick Colenbrander thunderbird2k@gmail.com 2009-12-04 06:39:24 --- This bug is not OSX specific it occurs on Linux as well. Most likely you are using Nvidia drivers which support both 24-bit and 32-bit visuals on Linux. Check the depth column in the glxinfo output.