power button/key ignored (ThinkPad T420)

Binary package hint: gnome-power-manager

In Ubuntu 11.04 Natty on my ThinkPad T420, the power button is ignored even though gnome-power-manager is configured to ask what to do when the power button is pressed. Neither of syslog, kern.log and dmesg have relevant logs.

Hard shutdown by pressing the power button for a long time works, but this is a hardware feature.

I'm not sure how to further debug this issue.

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: gnome-power-manager 2.32.0-2ubuntu2
ProcVersionSignature: Ubuntu 2.6.39-0.5~20110427-generic 2.6.39-rc5
Uname: Linux 2.6.39-0-generic x86_64
Architecture: amd64
Date: Wed Jun 15 16:16:47 2011
GnomeSessionIdleInhibited: No
GnomeSessionInhibitors: None
GnomeSessionSuspendInhibited: No
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110426)
MachineType: LENOVO 4180W1H
ProcEnviron:
 LANGUAGE=de:en
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-2.6.39-0-generic root=/dev/mapper/vgsys-root ro quiet splash vt.handoff=7
SourcePackage: gnome-power-manager
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 05/13/2011
dmi.bios.vendor: LENOVO
dmi.bios.version: 83ET56WW (1.26 )
dmi.board.asset.tag: Not Available
dmi.board.name: 4180W1H
dmi.board.vendor: LENOVO
dmi.board.version: Not Available
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnLENOVO:bvr83ET56WW(1.26):bd05/13/2011:svnLENOVO:pn4180W1H:pvrThinkPadT420:rvnLENOVO:rn4180W1H:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 4180W1H
dmi.product.version: ThinkPad T420
dmi.sys.vendor: LENOVO