After upgrading from 11.04 Natty to 11.10 Oneiric, I can no longer shutdown or reboot my system from within the GUI. I have to drop to a console and run 'sudo shutdown now' or 'sudo shutdown -r now' manually. When I choose the Shutdown item from the power menu in the top left corner of Unity's menu bar, and then click on either 'Restart' or 'Shutdown', it logs me out of X, then punts me to the LightDM login screen. From the LightDM login screen, if I try to shutdown or reboot, it just reloads the login screen. The box never reboots.

I am the only user on this machine. When I previously ran Natty, I used the Gnome classic interface rather than Unity. I've decided to give Unity a try, but if I have to jump through these kinds of hoops simply to reboot the system (e.g. after upgrades), then I wonder what the point is.