power management unable to put display to sleep

[Paddy Launch]

A recent update appears to have broken gnome-power-preferences. It is no longer capable of putting the display to sleep after a specified period of inactivity.
To reproduce:
1. start gnome-power-preferences
2. in tab "On AC Power" set "Put display to sleep when inactive for: " to 1 minute
3. wait 1 minute (10 minutes, 1 hour, or several hours)

What I expect to happen: display to switch off after 1 minute.
What happens: display remains active indefinitely.

This was working up until the last 7 days or so.

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: gnome-power-manager 2.30.0-0ubuntu1.1
ProcVersionSignature: Ubuntu 2.6.32-34.77-generic 2.6.32.44+drm33.19
Uname: Linux 2.6.32-34-generic i686
Architecture: i386
Date: Tue Oct 11 09:12:59 2011
EcryptfsInUse: Yes
GnomeSessionIdleInhibited: No
GnomeSessionInhibitors: None
GnomeSessionSuspendInhibited: No
InstallationMedia: Ubuntu-Netbook 10.04 "Lucid Lynx" - Release i386 (20100429.4)
MachineType: Dell Inc. Inspiron 1018
ProcCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.32-34-generic root=UUID=38d38be9-8acd-44f4-8519-f72dd828f186 ro quiet splash
ProcEnviron:
 LANGUAGE=en_GB:en
 PATH=(custom, user)
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
SourcePackage: gnome-power-manager
dmi.bios.date: 07/29/2010
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A01
dmi.board.name: 0GHG2G
dmi.board.vendor: Dell Inc.
dmi.board.version: A01
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.chassis.version: A01
dmi.modalias: dmi:bvnDellInc.:bvrA01:bd07/29/2010:svnDellInc.:pnInspiron1018:pvrA01:rvnDellInc.:rn0GHG2G:rvrA01:cvnDellInc.:ct8:cvrA01:
dmi.product.name: Inspiron 1018
dmi.product.version: A01
dmi.sys.vendor: Dell Inc.

[Paddy Launch (paddylaunch-deactivatedaccount)]

I have tested this with a second laptop and found that display
correctly turns off. The problem apparently only manifests on my
netbook.

[Paddy Launch (paddylaunch-deactivatedaccount)]

It now seems to work.