Have you updated to the AMD 13.4 drivers?
I have a Radeon HD 7850 in my workstation running Windows 7 x64, and I love the thing to death.
Trouble is, AMD hasn't released a driver worth a damn in nearly 8 months! 12.8 was good.
The good news is that some of the recent betas, and the Catalyst 13.4 release (2 days ago) seem to work well with Photoshop.
Thanks so much! I wish I had asked a long time ago. I kept right clicking on the drive listed in the Device Manager and choosing Check for Updates. And it kept telling me the driver was up to date. But I went to the AMD website and dowloaded the 13.4 driver as you suggested, and it appears to have fixed everything. Thanks again.