GTX 670 Graphics problems

Hey all,

Since a few days ago, I have been getting weird graphical glitches in-game, which definitely should not be occurring. At first I thought it was just Black Ops 2 Zombies, but it turns out it occurs in all games I've tried since (COD MW3, COD BO2, Assassins Creed 3). Turning up/down graphics settings does not change anything either. I have done a clean install of 306.97 drivers, 310.51 and 310.64, none of them solving my problems. I have even uninstalled and reinstalled the drivers completely, but no change either.
An example of the problems: https://www.youtube.com/watch?v=DO1wXaDdFKw
It basically just suddenly started occurring, is it RMA time?

My specs:
Asrock Z77 Extreme4 Motherboard
Intel Core i5 3570K
8GB Mushkin Blackline DDR3-1600 RAM
ASUS GTX670-DC2-2GD5 Graphics card
Seasonic M12II 650W 80Plus Bronze PSU

BTW: I am on Windows 8 64-bit, but it worked fine under Win 8 at first, so I doubt that's it.