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.