Following my previous comment, I have downloaded the source package for gnome-power-manager, compiled with --enable-debug=yes.
Now, when I press the power button it outputs the following:
(gnome-power-manager:3857): GnomeUI-CRITICAL **: gnome_client_request_save: assertion `client != NULL' failed
So it seems that the culprit is that gnome_master_client () is returning NULL.
Following my previous comment, I have downloaded the source package for gnome-power- manager, compiled with --enable-debug=yes.
Now, when I press the power button it outputs the following:
(gnome- power-manager: 3857): GnomeUI-CRITICAL **: gnome_client_ request_ save: assertion `client != NULL' failed
So it seems that the culprit is that gnome_master_client () is returning NULL.