What OS are you using? And maybe a small hope is turning off V-sync if its on.
I am using Google to try and track down information that can help, though helpful information is tough to track. Also what do you mean by unlocked the 4th AMD core? You overclocking? If so, how hot is your system?
I'm running Windows 7 Ultimate 64 bit edition
I am overclocking, as in Unlocked the core making it a quad core
It's running at 43 C, I have Arctic silver paste, and a coolermaster fan
My GPU is running at 62 C
Ok, ruling out SLI, cooling and up-to-date drivers.
Hmm, since as you said its with newer games, I'm guessing that its a problem with DirectX since Witcher 2 is more modern than WoW.
I'm afraid I'm stumped. I'd strongly suggest looking into the DirectX diagnostic tool. Go into start in the box at the bottom type "dxdiag" it should bring up the information of the system, let it check the drivers and hit 64-bit mode.
Try saving all the information, go into nVidea's forums and hope for the best with the dxdiag data.
I can only assume two things from this, A: DirectX 10/11 is glitchy with the card or B: There is a setting gone wrong somewhere.
You are not alone with this problem from all the similar threads to no avail.
Not sure if you checked this when you bought the vid card, but check the recommended amperage (amps) for your card, and verify that your power supply is generating enough amps to power the card + all your peripherals (hard drives, disc drives, usb devices, etc.)
MANY power supplies have the amperage split into several directions, leaving you with anywhere from 1/3 to 1/2 (or less) of the amperage you might need to run a powerful card. I had major problems with my rig when I first upgraded to a good PCI-E card. The recommended amperage for my card was in the 40's or 50's, and the power supply i had was generating TWELVE.
I ended up buying a corsair power supply, which had roughly the same wattage (550) but generated over 50 amps. I had replaced many parts, including my RAM and hard drive, before i figured this out. Haven't had a single problem since.