Thanks mate. I am also only running 2 x 1GB sticks, but cannot reproduce what you are running.

I think I just blew my PSU, it's making a quiet 'sizzling' sound, even when the PC is off but the PSU is still plugged in to power. There is no smell, just the sound. It still works, but I don't want to risk using it anymore. I am going to return it, and I am thinking in the back of my mind perhaps it has been the cause of my instability. I was stable for about a week, then the problems started and I couldn't pin them down.