Help! Computer Hard Reboots when running any games after 10 minutes

[mastermind85_33]

Hey everyone!
So all of a sudden since last night, everytime I run any stress tests or games, within 10-20 minutes the computer hard powers off out of nowhere. This is a brand new custom built system that has been working fine for several weeks now under heavy load. I have monitored the temperatures when this happens and the CPU temps never get above 58C and the GPU never gets above 78C. I have even reapplied thermal paste to the GPU to make sure. I tried rolling back the drivers, cleaning out any dust from the system, everything. Any other ideas what it can be? I am running a i7-2600k with a 500W corsair PSU and a 9800 GTX+ GPU. Any help is appreciated!!

 

[wolfram23]

Is anything overclocked?

And if not, were the RAM speed and timings set right?

 

[mastermind85_33]

The CPU and Vid card were overclocked, but I set them back to defaults and the problem still exists. CPU was overclocked using the Gigabyte Overclocker utility and the vid card using afterburner. Both were stable for weeks before this issue and still exists when set back to the default settings.

 

[mastrom101]

The two causes i can think of are cooling and power. You said that the cooling is fine, so thats probably not the issue. Maybe its the power supply?

are you overloading the 12v rail? If your PSu has two rails, try to balance them out. When did you build your system?

Im guessing its a PSu problem, but it could be a wiring, MOBO or cooling problem. Give me the details of the PSU