If you went to newer drivers other than the stock drivers that came with the card, did you disable the originals from the CD and delete them? Then loaded the new drivers you got from nVidia? That could be the problem too.
My son-in-law to be has the same card that he got for Christmas, and all is well with the stock CD drivers in MOH PA and other games. All he has is one exhaust fan in his HP computer so it's probably not heat related... just a guess on that.
Here a very good freeware utility for monitoring your computer's heat output....
http://www.almico.com/sfdownload.php
If it is heat related, get an Antec PCI cooling fan and install it under you GFX card. That will help cool the card even more, tho it's a large fan. Thermaltake makes one too that's a bit smaller and RadioShack here has them. Check where you are.