Ubuntu tweak crashes at launch: displays splash logo then error message

[Jean-Pierre Barboux]

Distribution: Ubuntu 11.04 natty
Application: Ubuntu Tweak 0.5.12
Desktop: gnome

Traceback (most recent call last):
  File "/usr/bin/ubuntu-tweak", line 110, in <module>
    launcher = TweakLauncher(session_bus, MainWindow())
  File "/usr/lib/python2.7/dist-packages/ubuntutweak/mainwindow.py", line 276, in __init__
    self.get_gui_state()
  File "/usr/lib/python2.7/dist-packages/ubuntutweak/mainwindow.py", line 351, in get_gui_state
    self.set_default_size(*TweakSettings.get_window_size())
  File "/usr/lib/python2.7/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/python2.7/dist-packages/ubuntutweak/common/config.py", line 35, in get_value_from_key
    return self.get_value()
  File "/usr/lib/python2.7/dist-packages/ubuntutweak/conf/gconfsetting.py", line 103, in get_value
    self.set_value(self.__default)
  File "/usr/lib/python2.7/dist-packages/ubuntutweak/conf/gconfsetting.py", line 112, in set_value
    self.__client.set_value(self.__key, value)
GError: Impossible de contacter le serveur de configuration ; la cause la plus fréquente est un démon D-Bus de session manquant ou mal configuré. Voir http://projects.gnome.org/gconf/ pour plus d'informations (détails - 1: Erreur lors du ping du serveur : IDL:omg.org/CORBA/COMM_FAILURE:1.0).