You may want to play with the registry in wine. I had two 7600 gt's working fine then upgraded to 8800 gt's which resulted in a few problems that were addressed by changing some values in the wine registry. See http://wiki.winehq.org/UsefulRegistryKeys
for more information. After I changed GLSL to disabled from enabled, my problems (slow video, low fps, anomlies during game play) were corrected.