Had a bit of a scare last night. Installed my new 1080Ti, booted up no problems. Ran a few 3DMark tests to make sure it was running as expected, no problems. Ran about 10-20 minutes of stress to test temperatures, no problems. Played about 30 minutes of WoW, no problems.
Then BAM....monitors shut off and go into power saver. I can still hear the game in the background, computer appears to be running fine other than the fact that I can't see anything. Re-seated the DP connections on both monitors, nothing. Cycled power on both monitors by pulling the power cable, nothing.
I powered off the computer, waited a few seconds, then powered back on. The fans on the 1080Ti revved up to full speed (it was LOUD). Let it do that for about 30 seconds to see if anything was going to happen but it kept on, so I powered it back down.
Opened everything up to see what was going on, nothing looked amiss. I took out the 1080Ti and put my 1070 back in. Since the 1070 takes only one 8-pin, I went to remove the extra 6-pin I had put in for the 1080Ti, just to get it out of the way, and to my surprise, the cable pulled right away from my modular PSU. Since I had the 1070 already in, I powered on, it worked fine. Swapped back in the 1080Ti, made sure every single power connection clicked in and was snug, then powered everything back on. Success, back in and working fine.
I guess the connector on the PSU slowly worked itself out since I didn't get it clicked in all the way. Lesson learned, I'm hoping that was the actual issue and not a red herring.