Run memtest first to rule out your RAM as the culprit, however I'm more convinced this is a PSU problem. You need to run prime95 under load and record how your rails are looking, if they're fluctuating like mad, or under/overpowered by 5%, you should be looking at replacing it.
I would also like to know what the rails current is rated.
Intel C2D E6320 / AMD Athlon X2 3800+
Gigabyte 965P DS3 / DFI nF4 Ultra-D
2GB OCZ Gold PC2-6400 / 2GB OCZ Gold PC4000
eVGA 8800GTS 320MB / eVGA 6800GS 256MB
150GB Raptor / 74GB Raptor
2x500GB / 320GB
OCZ GameXStreme 850w / OCZ StealthXStream 600w