Motherboard would be the first guess but did you think about the power supply ?What brand is it and how much power is in there. I can make a system fail one day and be okay the other day. Try with a really good psu (100w over what you have now + good brand) and see how it goes. If it's failling with that one, i would go for the motherboard.
- The Brownie
So it is the motherboard because, I have an AX750 and the other PSU was a CX700. Obviously Corsair is a good brand.
Also, THANK YOU so much for your help.