GTX 275 only artifacts in warhead at enthusiast settings

I have an EVGA GTX 275 and just beat the original crysis after playing for 5 hours straight (all high settings, 1600 x 1050, no AA, DX10) with not a single artifact (GPU temps were varied from 65C to 80C). As soon as I beat the game I installed crysis warhead and the game started with the settings auto set to gamer. Got about 2-3min into gameplay with no artifacting but when I decided to try turning the settings to enthusiast I immediately started seeing weird black lines whenever I would try to turn my character. I turned the settings back down to gamer and didn't see a single artifact. I check the GPU-z log after exiting the game and the max temp during gameplay was 79C which im pretty sure is fine.

The card is not overclocked at all.

Here are my specs:
Core i7 920 OC to 3.0GHz
Corsair 3GB DDR3-1333
ASUS P6T mobo
Antec 900 case
Corsair TX 750w PSU
EVGA GTX 275
Windows 7 64-bit RC

I have a pretty well ventilated case with all the case fans turned up to max speed and I don't think my gpu temps are anything outrageous either. Could it be that the windows 7 drivers are buggy with this card? I have no other artifacting whatsoever in my other games including the original crysis, just with warhead at enthusiast settings. Is there any chance that my card is bad?