1. (as root) mkdir /var/run/console
2. (as root) touch /var/run/console/ (Substitute in the user name of the user to be allowed to shut down the system for )

At this point, you will now have the menu available when you click log off, but all of the options will just log you off instead of actually shutting down or rebooting the system.

3. Make sure you have permission to run /sbin/halt as that user. One way (not necessarily the most secure, because this will let any user on your system shut it down by tying the command "/sbin/halt") is to run (as root) "chmod +s /sbin/halt".

The options on the log off menu should work now. If they don't, try running (as root) "ln -s /sbin/halt /usr/bin/halt".