Backlight brightness not reduced when on battery power

[Paddy Launch]

Binary package hint: gnome-power-manager

In Power Management Preferences under the "On Battery Power" tab, I have "Reduce backlight brightness" ticked. However, when I unplug the mains power from my Dell D830 laptop, the brightness remains unaffected (apparently indefinitely).

ProblemType: Bug
Architecture: amd64
Date: Thu Mar 25 16:00:58 2010
DistroRelease: Ubuntu 10.04
EcryptfsInUse: Yes
GnomeSessionIdleInhibited: No
GnomeSessionInhibitors: None
GnomeSessionSuspendInhibited: No
InstallationMedia: Ubuntu 10.04 "Lucid Lynx" - Beta amd64 (20100318)
MachineType: Dell Inc. Latitude D830
Package: gnome-power-manager 2.29.91-0ubuntu8
PccardctlIdent:
 Socket 0:
   no product info available
PccardctlStatus:
 Socket 0:
   no card
ProcCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.32-17-generic root=UUID=3d71c488-d372-4e57-916a-8610fe865967 ro quiet splash
ProcEnviron:
 PATH=(custom, user)
 LANG=en_GB.utf8
 SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.32-17.26-generic 2.6.32.10+drm33.1
SourcePackage: gnome-power-manager
Uname: Linux 2.6.32-17-generic x86_64
dmi.bios.date: 04/03/2008
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A11
dmi.board.name: 0HN341
dmi.board.vendor: Dell Inc.
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA11:bd04/03/2008:svnDellInc.:pnLatitudeD830:pvr:rvnDellInc.:rn0HN341:rvr:cvnDellInc.:ct8:cvr:
dmi.product.name: Latitude D830
dmi.sys.vendor: Dell Inc.

[Paddy Launch (paddylaunch-deactivatedaccount)]

Sorry, I was mistaken - everything is working fine!