http://bugs.winehq.org/show_bug.cgi?id=22478
--- Comment #7 from Roderick Colenbrander thunderbird2k@gmail.com 2010-04-26 09:08:55 --- I (hackily) fixed the shader issue just to make sure it isn't related to the performance drop. Whether I use the FBO patch or not I get a big performance drop within lets say 10 seconds in game when not using shadows. The same issue might also occur with shadows and thus might be the same issue you are seeing.