I had this problem years ago, and it took an RMA of my then 6950 to no longer have this issue. At first it started out randomly, maybe once a week. Now it's 6 times a day, regardless of what I am doing at the time of the freeze.
This issue is common across the PC world with no solutions. The fact of the matter is my EVGA 980 Classified simply does not play nice with the rest of my PC.
I know it's GPU related because of my previous experience with the problem and I have swapped #2 PC's 660 with the 980. #2 PC hasn't frozen in days, neither has sig rig.
Have used the past 4 nvidia drivers, including clean installations. Have even underclocked the 980 & have used different bios. I'm unsure of if I RMA because it doesn't get along with my system for some reason, but that doesn't seem right as the 980 appears to be fully functional & is running great in my other computer.
The freezes can be just watching youtube, or Folding @ Home, or Civilization 5, or Star Wars Battlefront. Doesn't seem to matter.
Curious as to if there are any other possible attempts at a solution before I've scratched all of my hair out.