[natty] GPM applet doesn't update "on power" status 30 minutes after power cable pulled

[Gavin McCullagh]

I have an Acer Aspire One (model zg5). When I pull the power cable, the acpi command updates output within a few seconds to

 Battery 0: Discharging, 91%, 06:14:30 remaining

However, even half an hour later, the GPM icon still says I'm on power. Also, the battery graphing utilities don't seem to be getting and useful data either.

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: gnome-power-manager 2.32.0-2ubuntu2.1
ProcVersionSignature: Ubuntu 2.6.38-11.49-generic 2.6.38.8
Uname: Linux 2.6.38-11-generic i686
Architecture: i386
Date: Wed Sep 14 09:16:59 2011
EcryptfsInUse: Yes
GnomeSessionIdleInhibited: No
GnomeSessionInhibitors: None
GnomeSessionSuspendInhibited: No
Lsusb:
 Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
 Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
 Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
 Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
MachineType: Acer AOA150
ProcEnviron:
 LANGUAGE=en_IE:en
 PATH=(custom, user)
 LANG=en_IE.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.38-11-generic root=UUID=ec98ddfb-6ff3-42ed-9543-7508e56b5447 ro crashkernel=384M-2G:64M,2G-:128M quiet splash vt.handoff=7
SourcePackage: gnome-power-manager
UpgradeStatus: Upgraded to natty on 2011-05-01 (135 days ago)
dmi.bios.date: 05/09/2008
dmi.bios.vendor: Acer
dmi.bios.version: v0.3301
dmi.board.asset.tag: Base Board Asset Tag
dmi.board.vendor: Acer
dmi.board.version: Base Board Version
dmi.chassis.type: 1
dmi.chassis.vendor: Chassis Manufacturer
dmi.chassis.version: Chassis Version
dmi.modalias: dmi:bvnAcer:bvrv0.3301:bd05/09/2008:svnAcer:pnAOA150:pvr1:rvnAcer:rn:rvrBaseBoardVersion:cvnChassisManufacturer:ct1:cvrChassisVersion:
dmi.product.name: AOA150
dmi.product.version: 1
dmi.sys.vendor: Acer