Originally Posted by tweaked
the 780i is likely the issue. unstable voltage BBQ'ing the cards.
Years of OCing that 780i have likely damaged it. I can remember a fair amount of posts on the NVIDIA forums where people had their 680 and 780 boards die or flake out after over volting them.
I have a 980a in my secondary rig now and have owned around half a dozen 680s and 780s with no issues, but I never over volted them.
My guess here is the 570s are more sensitive to the unstable voltage than the 470 was for some reason, the odds the OP got two defective 570s are pretty astronomically small.