BSOD whilst gaming

Hey guys I really need some help.
A month after I bought my Gigabyte 9800gt I bought crysis warhead and very occasionally whilst playing it online my computer would bluescreen. It's frequency has continued increasing to the point that I now cannot play Crysis Warhead online for more than 45 minutes without the display beginning to flicker and the FPS drop heaps and then the computer blue screens because nv4.dll or something like that has crashed. Now one other game crashes and BSODs sometimes. I really really need some help as I've eliminated software as the problem and reset my graphics card to stock. Please, you guys are my last chance. Specs are in my sig and I'll try anything to fix this. Thankyou in advance.

Temps are fine- 55C or so but the ram have no heatsinks and I ran a video ram test which it failed miserably. I've sent an email to the store I bought it from. Really depressed - first ever warranty claim on all of my many electronic devices. Not to mention I have little money. Will let you know how it turns out.