I'm having trouble with my Radeon 6770. The video output suddenly blacks out - no error messages just a black screen. Windows reports no errors just no video output so no option but to hard reset PC. Problem only happens in first 20-30 minutes after powering on. Once machine been running a while it doesn't seem to happen. Assumed it was a PSU problem so upgraded to a new PSU but problem persists.
System details below. Any help gratefully received as I'm out of ideas!