I just noticed that my screensaver has not been working, possibly since I upgraded to 10.6.3 a few weeks ago. Instead of kicking in, the screen just goes blank when photo screensavers should come on. When I go to System Preferences>Desktop & Screensaver>Screensaver, the button that says Screensaver just turns grey and nothing happens, and then if I try to press the back button or Show All, it wont go back. (At this point in order to get System Preferences to work, I have to quit it and open it again.) If at this point I press the Desktop button it turns grey too, though I can successfully press on the pictures and bring up new desktop pictures.