DBUS error when invoking

[Mark Eduart <lavafire gmx de>]

Hi

I have been using a small stolen script which is called by udev and 
locks the screen if i unplug a usb-key.
It used to work just fine. Unfortunately i cannot remember when it 
stopped working. Somewhere in F17.

I am using:
o Fedora 17
o with 3.6.x Kernel
o gnome-screensaver 3.4.1

The screen locking itself works just fine if enter the following 
directly on the shell.
I use the same commands in my script, where they dont work.

gnome-screensaver-command --lock

or

dbus-send --session --dest=org.gnome.ScreenSaver --type=method_call 
--print-reply /ScreenSaver org.gnome.ScreenSaver.Lock


Started with debug and in foreground, gnome-screensaver throws a dbus 
error message:

[listener_dbus_handle_system_message] gs-listener-dbus.c:854 
(11:40:08):         obj_path=/org/freedesktop/login1/user/1000 
interface=org.freedesktop.DBus.Properties method=PropertiesChanged 
destination=(null)


Does someone have an idea what is wrong / what i am missing ?
Or do i just have a DBUS problem ?

Thank you.
Mark