I was experiencing this exact problem for quite a while (Photoshop CS4 64-bit on Win7 64-bit) and tried all kinds of things to fix it, fiddling with every remotely-relevant Photoshop setting there was, along with various Windows compatibility options, none of which made any difference.
In the end I tried completely uninstalling my (ATI/AMD Radeon HD 5670) graphics card drivers from Device Manager, forcing Windows 7 to revert to using its own built-in drivers (the ones listed in Device Manager as provided by "ATI Technologies Inc.", dated 9th November 2010 and with version 8.792.0.0). I've now been running everything with that driver for the past month and haven't had any more problems with Photoshop since then.
Clearly, reverting to stock graphics drivers is far from ideal if you use that computer to play games or anything like that, but as this is my work PC, the built-in driver works perfectly for my purposes.
(Of course, this could just be yet another one of the myriad solutions that people have found to fix this issue but which don't work for anyone else! Hopefully this will help at least one other person, though...)
Edit: Curses, Photoshop's just gone back to refusing to do anything. I'm beginning to wonder if this is an issue with faulty RAM or something, but for now all I can say is that reverting my graphics drivers doesn't seem to have solved the problem after all.