Comment 10 for bug 207157

This was removed in the last version of dbus ( 1.1.20-1ubuntu1 )

From the Change log:
     - debian/rules: Do not install /etc/X11/Xsession.d/75dbus_dbus-launch, we
      do not need it for Gnome, KDE, and XFCE, and it causes trouble.
      (LP #62163)
    - debian/dbus.preinst: Remove obsolete conffile
      /etc/X11/Xsession.d/75dbus_dbus-launch on upgrades. This needs to be
      kept until after Hardy's release.

I think you need to add the following to your .xsession if you are not using KDE,Gnome or XFCE

if test -z "$DBUS_SESSION_BUS_ADDRESS" ; then
 ## if not found, launch a new one
 eval `/usr/bin/dbus-launch --sh-syntax --exit-with-session`
fi