When I am have the power adaptor unplugged in, closing and opening the lid won't make the screensaver activate. This works fine with the laptop plugged into the wall.
Just to clarify: - your laptop is running on battery - your g-p-m is set to blank screen on lid close ? And it doesn't work ? Works fine here...
*sigh*. Works after a reboot. I'll reopen if I can reproduce.