Shutdown/Reboot Ubuntu

How do you shutdown/reboot Ubuntu from ROX-Session?

Logout works fine in home-built ROX-Session 0.41.0 (unlike in 0launch
ROX-Session where even Logout is broken) but Shutdown or Reboot does
not. No problem in Debian Lenny/Squeeze/Sid so I guess this might be
related to Ubuntu's disabled root account but I have no idea how to
fix it.

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