I have a computer with an HD 7950 I bought a month ago and it suddenly started showing artifacts today in Crysis 2. I posted a video of it up on youtube, and you can see it here: http://www.youtube.com/watch?v=d4XXPv7iwLI
I'm wondering if there could possibly be some other cause other than a video card failure, since this is relatively new and I didn't expect the video card to have problems so soon.
First, test it with Furmark under Burn in for about an hr and use MSI Afterburner and/or GPU-Z to monitor the temps to see if it's overheating. You can also try reinstalling the GPU driver, make sure you uninstall the current first, reboot, then install the latest.