I think this is due to Compiz. I've just tried it with Compiz switched off and all is well.
-- Screensaver does not come on automatically https://bugs.launchpad.net/bugs/275390 You received this bug notification because you are a member of Ubuntu Desktop Bugs, which is subscribed to gnome-screensaver in ubuntu. -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs