So I'm having a slightly different problem with mine, but I'm wondering if it's the same underlying issue. Here's how it went.
I pre ordered a GTX 1080 FTW and finally got my card in mid july and it's been working flawlessly for more than a month. Boosts itself to 2012mhz without me even touching it. Mid-late august I booted up the witcher 3 and noticed some strange graphical glitches after teleporting. It wasn't anything major, just some plants missing textures, and it went away once I restarted the game. A few days later while playing GW2 after changing maps I noticed some visual artifacts covering the top part of the screen, alt tabbed and it was gone. This happened once more since, but other than that nothing was out of the ordinary. The temps hovered around 50-65C, never even getting close to 70C, and everything ran smoothly. Until yesterday.. I left the PC for 15-20min while making dinner and when I got back upstairs the screen was black and the fans were spinning like crazy, nothing I did helped so I had to do a hard reboot. Now when I booted the PC back up the card was dead. Literally dead. The fans weren't spinning, the LEDs were off, and the monitor didn't recognize the card, but I could hear that the PC itself was working fine, the windows bootup sound played and everything, and the PC was completely fine once I plugged the monitor into the mobo.
I've tried everything I can think of, I swapped PCI-E cable, tried another PCI slot, even threw my old GTX 660 into the PC just to make absolute sure that the GTX 1080 was the issue.
I'm not sure if it's the same issue described in this thread since my card just flat out died, but now I'm at a loss.. I've set up an RMA request with the retailer I bought the card from and now I'm just waiting and hoping I'll have better luck with the new card. :/