Session locks-up completely when computer is idle

Session locks-up completely when the computer is idle for a while on Ubuntu 11.04 using a Toshiba NB200 netbook. It could have something to do with gnome power management, but so far I have not been able to prevent the bug by changing different settings.

Ubuntu release: Ubuntu 11.04

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: gnome-power-manager 2.32.0-2ubuntu2
ProcVersionSignature: Ubuntu 2.6.38-8.42-generic 2.6.38.2
Uname: Linux 2.6.38-8-generic i686
Architecture: i386
Date: Mon May 16 00:16:59 2011
ExecutablePath: /usr/bin/gnome-power-preferences
GnomeSessionIdleInhibited: Unknown
GnomeSessionInhibitors: Failed to acquire
GnomeSessionSuspendInhibited: Unknown
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Beta i386 (20110413)
MachineType: TOSHIBA TOSHIBA NB200
ProcEnviron:
 LANGUAGE=nl_NL:en
 LANG=nl_NL.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.38-8-generic root=UUID=90236c8a-c22f-49ba-82eb-3041688dea1a ro quiet splash vt.handoff=7
SourcePackage: gnome-power-manager
UpgradeStatus: Upgraded to natty on 2011-05-15 (0 days ago)
dmi.bios.date: 04/07/2009
dmi.bios.vendor: TOSHIBA
dmi.bios.version: V1.20
dmi.board.name: KAVAA
dmi.board.vendor: TOSHIBA
dmi.board.version: 1.00
dmi.chassis.asset.tag: *
dmi.chassis.type: 10
dmi.chassis.vendor: TOSHIBA
dmi.chassis.version: N/A
dmi.modalias: dmi:bvnTOSHIBA:bvrV1.20:bd04/07/2009:svnTOSHIBA:pnTOSHIBANB200:pvrPLL20E-00200HDU:rvnTOSHIBA:rnKAVAA:rvr1.00:cvnTOSHIBA:ct10:cvrN/A:
dmi.product.name: TOSHIBA NB200
dmi.product.version: PLL20E-00200HDU
dmi.sys.vendor: TOSHIBA