radeon fps problem

Hello there!
This thread is opened cuz i have 1 friend with that problem.
He have ATI Radeon HD 3650 AGP - 512mb , 1GB ram , 1.8Ghz processor and his fps drops alot and got some lag on some moments (shooting not jumping) can someone of u guys give some advice? thx..

Bump because I'm also having this problem.

Got a Radeon HD 4670 and I get fps drops when looking at or near an ambient light (i.e. when someone turns on their flashlight, or the light in the second room of kz_ruins). I used to have this problem with my old card (Radeon x300/x550) but that didn't happen until about a year ago.

Also omilo has a Radeon HD 4870 (I think) and doesn't have this problem, so I have no idea what's up with it.