I have tha same card but different manuf. I also had that same problem just the other day and here is what I did. I DL'd the new version of Driver cleaner pro and ran it twice in safe mode using only nvidia as a filter/criteria. You may need some thing different... you will want to do your ATI and whatever nvidia drivers you have. After a reboot I installed the Xtreme-G 96.89 drivers they are geared towards gaming and benching.
There is also a thread about unlocking some pipes and it is debated. I can't say if I unlocked any pipes but I can say that after doing it I can run games at a higher quality settings without lag.Here is a link to the thread
WOOOOOO thanks alot this worked brilliantly! i can now have realy high settings with hardly any lag. The only thing is everything runs fine appart from cod UO it still lags with explosions and stuff and i dunno why :S?