Diffnetly either something overheating(could also be a RAM module not seated properly check everything!), power supply not providing enough to the 12v rail would also be a reason for this, or power supply dieing or the power rectifier on the motherboard is dieing(Do you have lots of power outages were you live, this could cause that.)
Hmmm no power outages. But the Power Supply was the one thing I did not upgrade when I upgraded everything else. This was because the wattage on the PSU was quite a bit over the requirements for everything I bought in the documentation. I'll consider picking up a better one though.