At some point during the Jaunty test cycle shutting down and rebooting the machine stopped working with the Action Buttons menu applet – It would fail with the message “Unable to perform shutdown” and some HAL-related messages.
While annoying I didn’t put any real effort into solving the problem, until today.
I didn’t have to look long though as the answer was in the Arch Linux forum.
Open the file /etc/PolicyKit/PolicyKit.conf
and add these lines
<match action="org.freedesktop.hal.storage.mount-removable">
<return result="yes"/>
</match>
<match action="org.freedesktop.hal.power-management.shutdown">
<return result="yes"/>
</match>
<match action="org.freedesktop.hal.power-management.reboot">
<return result="yes"/>
</match>
Add them inside the config stanza.