Since upgrading to Ubuntu Gutsy I've occasionally been seeing the following notification from GNOME Power Manager:
I'd usually trigger this error by unplugging the AC adapter and then picking suspend from GPM's left click menu.
My first thought on seeing this was "What's a policy timeout, and why is it not valid?" followed by "I don't remember setting a policy timeout". Looking at bug 492132 I found a pointer to the policy_suppression_timeout gconf value, whose description gives a bit more information.