can't shutdown from gdm

[Dr. Michael J. Chudobiak]

I have F9 installed on an HP DC7700.

Clicking the Restart and Shutdown buttons has no effect from the gdm 
greeter. I get these errors:

Jul 24 08:24:51 caprica gdm-simple-greeter[2418]: WARNING: Unable to 
find users: no seat-id found
Jul 24 08:25:13 caprica gdm-simple-greeter[2418]: CRITICAL: 
dbus_g_error_get_name: assertion `error->code == 
DBUS_GERROR_REMOTE_EXCEPTION' failed

How can I fix that?

- Mike