I know this thread is a little bit old, but in case anyone else ends up here like I did, trying to solve this problem, I think I can offer a little more guidance. Using the ShellExView program linked above, in my case anyway, the apparent culprit turned out to be "DivX Property Handler". I tried disabling the DivX Thumbnail generator first, but it didn't help. Disabling "DivX Property Handler" definitely solved the problem, though. Your case may be different, I don't know.