How are you running that -- is there a native version (I wouldn't know), do you use Wine, Cedega or what? Cedega is supposed to work better with games than Wine, but even after that you'll need to make sure you have direct rendering enabled (run glxinfo) and that it's actually helping you (run glxgears with fps showing up). For nvidia cards use nvidia proprietary drivers, for ATI use fglrx; you should get glxgears run pretty smoothly before trying out 3d games.
If you're using Cedega (and paying for it), you can get the support from them. If you're using Wine, it might be just that.