crysis problems

ok i have a problem that i have never had before this week. EVERY time i start crysis, it starts fine, and gets to the main menu. no matter what i do (even if i just leave it at the main menu and do nothing) my computer crashes in about 30 seconds or less. i have no idea what the problem is. i am on patch 1.1 and have not updated to whatever latest patch there is but i dont think this is the problem considering its played fine for weeks before this. i WAS overclocking a bit but as soon as this started happening, i went back to stock clocks and it still happened (note: i have NEVER had any overclocking problems). i have the most recent nvidia drivers.

system:
AMD phenom 9850 quad core (2.5 ghz)
2x 8800gt (512mb) in sli
4gb ram
vista ultimate

what do you mean sensitive to overclocking?

yes i did OC my CPU. i ran stability tests. my system is stable at 2.75ghz. i rarely OC my gpu's but i have before (i dont find the need to, my sli setup plays anything i can trow at it). Overclocking is not the problem right now considering that i have put my system back to stock clocks and i am still having the same problems. i have no problem with heat, i have a large case and 5 case fans. cpu never goes over 55C and gpus never over 75C.

maybe i did not make it so clear in my initial post, but the reason i posted this is because I am having problems even when i AM NOT overclocking.

NOTE: crysis has played absolutely fine (for the most part) up untill about saturday. then it started bugging out. i re installed it and no better luck.