BSOD randomly happens

Thanks to all the help I have got from this forum, I hopfully have now solved the BSOD problem (well it's been stable for a few days now !)

It turns out the DDR3 was bad.

I did run memtest86 for 11 passes and got no errors at all.
I ran Prime95, the test recomended here which is small FFTs for about 3hrs and still no errors.
I then had a play with Prime95 and ran the blended test, so a range of FFTs that ment the ram is used a lot more, within a few mins each of my 4 cores came up with a rounding error !

I then did the same test with only one DDR3 stick at a time and found one to be at fault.
So, I got some new DDR3 (same speed/latency) and all is stable now.

I am a little concerned that Memtest86 did not pick this up, very strange, but at least I have a stable system now !!

Cheers.