Comment 3 for bug 702418

James Adney (jfadney) wrote :

I don't have time to try and tackle this, sadly, but I did notice something potentially useful:

Part of your problem could actually be a bug in update-manager.
update-manager tries to use the org.gnome.PowerManager interface to inhibit sleep before it tries the freedesktop standard (org.freedesktop.PowerManagement) that xfce-power-manager uses. This could start gnome-power-manager unnecessarily.

That may not fix your problem completely, but it's a start.

As posted earlier, you should be able to just get rid of gnome-power-manager to fix this problem.