I'm having a really really annoying graphical issue that I cant seem to find a fix for, I've searched and searched and to no avail. I can't really recall when the problem started happening but as far as I know it WAS NOT happening after a fresh install. Anyway, I've checked temps I have reinstalled drivers and still cannot seem to fix this issue.
If you are overclocking either your CPU or GPU, revert back to your stock settings and see what happens. You should also make sure that all of your fans are working properly and are clean (no dust bunny or hairball buildup, including the power supply).
To troubleshoot futher, we would need a complete listing of your system's components to begin to resolve the issue. You are describing a classic heat or power issue as indicated by the artifacting.
So I found that ATI-Overdrive was on, I turned that off, rebooted all that.. and I thought it was good for a while! But they returned : ( Temp's are the same with and without overdrive, so I'm not sure what the deal is.