Comment 2 for bug 547166

I believe this is affecting me too. When the screen saver comes on and has been on for a while (overnight in this case) mouse movements and keyboard do not bring up unlock screen. I do see mouse move on screen. I was able to SSH in and killall gnome-screensaver and then I could get back in.

gnome-screensaver then restarted and top showed 2 processes both with 98-99% of cup. Had to reboot.