I have the same probelm with quake 3. My gamma is all borked. But i can fix with in game slider. Now this floored me. I play Urban terror (q3 mod) only. Now before i could play 1280x1024 w/2x AA and 2x AF and get about 60-70fps. If i went above that IQ i would get ~35-40fps and lag. Just for the hell of it i changed to 4x AA and 8x AF and at the same res. im getting the same FPS ~60-70 and looks great albeit the gamma thingy. Now thats amazing. Sucks they do this now after i just ordered my radeon 9700 (which is in the mail now) just for the IQ. Oh, well. Cant win em all. Also, my ti4600 is NOT overclocked.
Intel p4 email@example.com
512mb Corsair pc 3200@2 CAS
Visiontek geforce 4 ti 4600 @stock speed
Winxp PRo v2600