about policy

[Bear]

hi,
These days, I have run into some trouble on dbus on FreeBSD. It seems that dbus stop transferring so many messages. For example, if I run this command as a normal user(not root):
dbus-send --session --dest='org.gnome.SessionManager' --print-reply --type=method_call /org/gnome/SessionManager org.gnome.SessionManager.CanShutdown

It would responsed nothing. Even if a normal user have no right to shutdown, it should return a 'refuse' message. When I tried this on Linux, I can got response.  Because I am not familier with dbus and its default policy, so could you give me some advise or tips on this?

--------------
Bear
2010-07-23