I have a problem with multiple games (World War Z, Modern Warfare). As you can see from this video (not mine but this is what it looks like) there seems to be some pixel stretching happening. I tried underclocking but the problem still persist. I think it's not a problem of overheat though, since in Modern Warfare, the problem happens right after opening the game. In WWZ though, it will happen after a while, like an hour or two.
Have you tried the troubleshooting steps listed here?
Troubleshooting Common AMD Graphics Driver Installation Problems
If these don't fix the issue then most likely your graphics unit is faulty and you should proceed an RMA