run memtest to see if it is your RAM. 2 instances of Super Pi for your CPU.
Are you running that RAM @ DDR800? If so, that shouldn't be whats causing the instability, but if you are running it with the 2.5 multi (DDR1000) then you may be having problems there, I have the same RAM and can't get mine that high even with 2.3v.
Give more info as well.
Whats your vCore?
vDimm?
RAM timings?
Motherboard?