I utilize both a screen saver and the show desktop feature but have never seen this problem in the past. You might play around with your screen saver settings to see if they have any affect. You might also try another computer just to make sure something larger scale isn't going on. Also, testing with other programs to make sure it isn't a general OS issue is always a good idea. Other possibilities include changing your Video Driver settings, updating your video driver, and uninstalling - reinstalling.
