Possible Duplicate:
Ubuntu 11.10 logs off when clicking shutdown
When I need to reboot (sadly, the days of 300+ days of uptime appear to be long gone) while logged into my account, the Shut Down option only logs me out - it does not shutdown the system.
When at the login screen, selecting the shutdown or restart option does nothing - I get a dialog box, but regardless of which option I select, nothing happens.
Interestingly enough, when I first boot up, selecting shutdown from the login screen works, as long as I haven't logged in yet.
Is this a known problem? Any way to figure out how to fix it?