This happens because of a change in Gnome : Gnome now uses a "Gnome Control Center". A link to it should appear in your System menu.
Please reboot and see if it does appear. If it does run "mv ~/.config/menus/system.menu ~/.config/menus/system.menu.undo-1" in a Terminal. -- System Menu options dissapear https://launchpad.net/bugs/79576 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
