I, too, suffered from this issue for many days. I tried the DontRefresh registry fix, but it had some nasty side effects. One was that IE would constantly refresh and flicker when viewing web pages. Obviously, I reset the registry key to its default value.
I didn't have any significant 3rd party windows explorer extensions.
I reset all of the Windows Explorer -> Folder Options to default settings.
I reset my Theme to the Windows 7 Default theme.
Still had the problem intermittently.
Wait for it........ I rolled back my video driver (which was an ATI driver obtained through Windows Updates). VOILA! The problem has disappeared.
So, I went to the ATI website and obtained their latest Catalyst driver release which they maintain is Win 7 compatible (how long did it take them?). Installed it and all has been well for a few weeks now.
It seems that the rollback of the video driver resolved the issue. The installation of the ATI version did not cause the issue to reappear. So I'm going to forego installing the Windows Update recommended ATI driver until...well probably for good.
I had similar issues with recommended ATI display drivers in Vista. Getting the drivers straight from ATI seemed to usually resolve my issue.