@coinits You should try to hook up a differnt psu. Simple thing to do and you don't need a big one, just enough to run 2 cards to verify if its the psu or not. 450-500w should do it.
What kind of risers are you using?
I'll try the PSU. I have a Corsair 750 that works fine. There are no risers. I have a GA-X79-UD3 from Gigabyte which has 4 slots.
Are your cards ones that are mb power only?
If so that might be the issue. Too much power on the mb
Nope they powered by the PSU. This rig was spec'd out on here and this worked perfect for over 1 month.