atljsf :
the first thing that comes to mind is the psu here
the sli, is it necesary? can you do a test with 1 980?
Regarding the 2x980s......ABSOLUTELY!!! Nvidia claimed that the 1080 is faster than a 980 SLI, but the website and YouTube reviewers showed that this is not always the case; i.e. the 98 SLI and 1080 are very close together (minus 4GB GDDR5..).
About 2hrs ago, I was at my wit's end and couldn't think of anything else to do, so I removed the 4 GB DIMM from the B2 slot on the mobo, leaving the other 4GB DIMM in the A2 slot. It absolutely stymies me....but in the past two hours of playing Diablo 3, the computer has been perfectly fine. As I write this, I just turned the system back on after a shutdown to reinstall the second 4GB DIMM. That was about 20min ago. Still working fine...
That leads me to think that the problem was/is localized to the system RAM, either that particular DIMM or slot B2. I've had GPU issues before (the first 980 had to be RMA repaired because it wasn't working), Windows issues, and CPU issues (OC instability when I thought I had it dialed in perfectly). But never RAM issues. But now all is well...
I don't know if any of this helps. It's great that it's working again, but I worry about a "relapse", and I'd like to know what the issue was..