It would start with the PSU!!!!! Swap it out with another form a friend whatever and see if the problem persists. If it does then we'll have to look at other issues such as memory or mobo ground leakage voltages etc. which I will coach you on if you arn't aware of PSU back testing proceedures.
Noli Nothis Permittere Te Terere!!
EVGA 680i, Dual EVGA 8800GT'S (650/950), 4 gigs OCZ DDR2 1066, Intel Q9450 at 3.8 Ghz, Koolance Water Cooled, Dual Plextor16x DL DVD+/-RW. Dual WD 250gb 16mb Cache Sata 3.0. 3DMark06 score = 19,168.