it crashes at startup

[Mehrdad]

Distribution: Ubuntu 10.10 maverick
Application: Ubuntu Tweak 0.5.10
Desktop: gnome

Traceback (most recent call last):
  File "/usr/bin/ubuntu-tweak", line 110, in <module>
    launcher = TweakLauncher(session_bus, MainWindow())
  File "/usr/lib/python2.6/dist-packages/ubuntutweak/mainwindow.py", line 276, in __init__
    self.get_gui_state()
  File "/usr/lib/python2.6/dist-packages/ubuntutweak/mainwindow.py", line 351, in get_gui_state
    self.set_default_size(*TweakSettings.get_window_size())
  File "/usr/lib/python2.6/dist-packages/ubuntutweak/common/config.py", line 147, in get_window_size
    width = cls.config.get_value_from_key(cls.window_width, default=900)
  File "/usr/lib/python2.6/dist-packages/ubuntutweak/common/config.py", line 35, in get_value_from_key
    return self.get_value()
  File "/usr/lib/python2.6/dist-packages/ubuntutweak/conf/gconfsetting.py", line 103, in get_value
    self.set_value(self.__default)
  File "/usr/lib/python2.6/dist-packages/ubuntutweak/conf/gconfsetting.py", line 112, in set_value
    self.__client.set_value(self.__key, value)
GError: Failed to contact configuration server; the most common cause is a missing or misconfigured D-Bus session bus daemon. See http://projects.gnome.org/gconf/ for information. (Details - 1: Server ping error: IDL:omg.org/CORBA/COMM_FAILURE:1.0)