Hey people, I also have this problem.
I sent my first card back about a week and a half ago because of coil whine. Tried loads of stuff to get rid of the coil but no luck (new psu, burn in test etc).
I just got my rma 1080 FTW replacement yesterday and unfortunately that also had the same level of coil whine ..so I though I would learn to live with it rather than yet another rma.
So I booted up the heaven benchmark for the first time with the new 1080 ftw. After 15min of running the bench I got a black screen and a hoover like fan noise from the card.
The card reached about 70°c on ultra, and about 55-60°c on low settings with a lower resolution ..all setting resulted in the same black screen fan problem after about 15-20min running heaven.
Tried just about everything to get it working, I lastly used debug mode via the Nvidia control panel and still no luck.
I did not have this problem with my first card and I haven't changed anything in my system since. I now wish I didn't rma my first card, but you don't really expect anything like this to happen I guess.