Ever since upgrade to Tiger, I cannot run screensaver without ending up with a black screen and a white arrow after a few minutes, with no control of anything apart from ability to move the white arrow around the black screen - but no wake-up and no return to active screen or sleepsaver screen. Restart on G4 tower is only option at this point. I have checked screensaver and energy prefs-- no conflicts apparent. I see scattered Internet posts about this problem, but no evidence it is a known Tiger bug that Apple is trying to get fixed. My current cure for the problem is turn off the Apple screensaver, but I'd like my screensaver back, not black.