Are you using external monitors ? Having laptop lid closed ? Then this bug might be it: http://bugzilla.gnome.org/show_bug.cgi?id=365016
-- g-p-m failing to use DPMS to power off display https://launchpad.net/bugs/34233 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
