Major Graphics Artifacts

While playing Crysis for about an hour, my screen just started to go berzerk. I got a bunch of random polygons (it was too bad for me to get a screen shot). I thought it was a heat problem but when I managed to get the nvidia monitor on screen and finally by luck read the temp, it said only 68 celsius. although it was rapidly cooling to 60.
I have a 8800GTS 320 XFX XXX edition 560/1700. 2GB RAm P5N-E SLI and E6750 stock. What do you think the problem is? I'll try and run it again and get a screenshot if possible.

FYI i just barely managed to turn it off without doing a hard reboot. (by selecting the windows turn off)

68C is perfectly fine for an 8800 GTS. Some people run them up to 90C without having an issue and the radeon 4000 series can run hotter yet. Your fx 5500 is a completely different graphics card designed to run differently, its temperature threshold cannot be compared to a more recent card.

OP, If it keeps happening, try checking your video ram temperatures instead of the core temps. GPU-Z can tell you that information.