Ubuntu 9.10 doesn't suspend when closing the lid on batteries

In Jaunty you were used to shutting the laptop's lid and trusting it would go to sleep... Well, not any more in Karmic. I've already done it several times only to find out that the poor laptop was cooking in its bag, or just shut itself down after running out of batteries.

The problem is related to a massive refactoring of gnome-power-manager, which now uses the devicekit-power daemon instead of the recently deprecated hal. Particularly, the problem has to do with the inability of devkit to determine whether we're on AC or battery reliably.

Luckily, you can get the fix from this ppa:

sudo add-apt-repository ppa:jmartinj/dkp
sudo apt-get update
sudo apt-get upgrade

Hope it works for you!