Open the file /etc/dbus-1/system.d/hal.conf
and add this policy:
<policy group="plugdev">
<allow send_interface="org.freedesktop.Hal.Device.SystemPowerManagement"/>
<allow send_interface="org.freedesktop.Hal.Device.LaptopPanel"/>
<allow send_interface="org.freedesktop.Hal.Device.Volume"/>
<allow send_interface="org.freedesktop.Hal.Device.Volume.Crypto"/>
</policy>
Now just run
/etc/init.d/rc.hald restart
and enjoy!
I tried it in Thunar.
I found the information here.