I tried changing the setting: sleep when inactive, from never to 1 hour just as an experiment. The screen saver started working! Also, interestingly enough, when I let the system sit for an hour, it went to sleep as it should. But then, when I hit the button to wake it up, I was not asked for the password! Previously, I had tried to make that happen with the manual sleep routine, avoiding entering the password every time I woke it up. Has anybody noticed this behavior on their laptop?