Ubuntu failing to warn about low battery

Binary package hint: devicekit-power

Description: Ubuntu karmic (development branch)
Release: 9.10

devicekit-power:
  Installed: 011-1ubuntu1
  Candidate: 011-1ubuntu1
  Version table:
 *** 011-1ubuntu1 0
        500 http://archive.ubuntu.com karmic/main Packages
        100 /var/lib/dpkg/status

What I expected

1) Unplug AC cable
2) The icon in the gnome panel shows how the battery discharges over time
3) When battery gets low I get warned

What happened

1) Unplug AC cable
2) The icon always shows 'almost full' (looks like 90%)
3) I don't get a warning and the computer just shuts off (it doesn't shut down ubuntu properly, the screen just goes blank instantly)

Fortunately I had no unsaved data at that time, but it was scary and could've cost me a lot of time if I had anything unsaved!