Comment 8 for bug 863834

Guys, I found the origin of "problem". Gnome3 changed your politics about power management and now, when an external monitor is connected, gnome-settings-daemon doesn't suspend/hibernate the laptop. See it: http://blogs.gnome.org/hughsie/2011/02/02/is-gnome-3-going-to-melt-your-laptop/

So, either close the bug or convince the gnome devs change this behavior.