Hey
I recently had the same problem with my XFX Radeon 5770. Read all the online 'issues' with it, tried all posted workarounds that helped anyone,
then based on that assumed it was the vid card too. I opened ticket with xfx help desk to pursue the RMA process.
They helped me troubleshoot it. It wasn't the card. The first tech said not the card, install this program and that to get my temps, try new higher rated psu etc....
The 2nd tech was bang on, he suspect memory controller errors. I had latest version of MemTest 86 ready to go - This led to the problem, my ram.
Pls download the most recent version of MemTest86. Let it run for at least an hour or so.
Any errors with the ram or 'correctable' memory controller errors' ?