Re: PSU or Motherboard problem?
I had this problem an it ended up being my psu that was faulty , however just changing the psu did not fix it as it damaged my motherboard. (NEVER BUY A CHEAP PSU...lol)
Do you have a computer store that could test the psu for you.
Or could be something over-heating and its powering off to prevent damage.
I5 3570k oc'd 4.3Ghz, CM hyper 212+cooler, Gskill 8gb 1600Mhz, Gigabyte 7970hd oc edition, msi z77a-g45. Samsung 830 256gb SSD, WD cavier black Hdds