Why am I unable to Restart or Shutdown my computer from the LightDM login screen?

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http://askubuntu.com – I'm not sure whether this is a bug (in which case I'll submit a report) or I'm doing something silly! My problem is that I cannot restart or shutdown my computer from the LightDM login screen, this problem occurs if I go through the following steps: Log in Lock the screen either through inactivity or selecting "lock screen" At the password entry screen select "Switch User" Click the power symbol at the top right of the LightDM login screen and select "restart" or "shutdown" When I do this nothing happens, the computer does not restart or shutdown and neither is there any error messages, (HowTos)