This has been happening randomly since our switch to the lovely Ubuntu server platform. The open bugs at launchpad were a good starting point for information.
What seems to be happening is that the dbus service is crashing and this is evident because the gnome-power-manager service is a screamer and depends on it, so after we restart dbus(#/etc/init.d/dbus restart) two instances of console-kit-daemon are running and fighting with each other for control.
The simple solution was to kill one of them:
$ps aux | grep console-kit-daemon and sudo kill xxxx
$pidof console-kit-daemon then pick one and kill it or script it to be killed.
We will see if this helps.....