Reboot function not work on DELL machine.

[Sharl.Jimh.Tsin]

as the title.

the button "reboot" never work on DELL OptiPlex 790 desktop.

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: linux-image-2.6.38-10-generic 2.6.38-10.46
ProcVersionSignature: Ubuntu 2.6.38-10.46-generic 2.6.38.7
Uname: Linux 2.6.38-10-generic x86_64
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.23.
Architecture: amd64
ArecordDevices:
 **** List of CAPTURE Hardware Devices ****
 card 0: PCH [HDA Intel PCH], device 0: ALC269VB Analog [ALC269VB Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: sharl 1646 F.... pulseaudio
CRDA: Error: [Errno 2] 没有那个文件或目录
Card0.Amixer.info:
 Card hw:0 'PCH'/'HDA Intel PCH at 0xe1a60000 irq 45'
   Mixer name : 'Intel CougarPoint HDMI'
   Components : 'HDA:10ec0269,102804ad,00100100 HDA:80862805,80860101,00100000'
   Controls : 22
   Simple ctrls : 13
Date: Mon Aug 1 19:56:59 2011
EcryptfsInUse: Yes
HibernationDevice: RESUME=/dev/sda2
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1)
IwConfig:
 lo no wireless extensions.

 eth0 no wireless extensions.
MachineType: Dell Inc. OptiPlex 790
ProcEnviron:
 LANGUAGE=zh_CN:en
 PATH=(custom, user)
 LANG=zh_CN.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.38-10-generic root=UUID=dce5ed30-b95c-486d-900c-851fac15d968 ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-2.6.38-10-generic N/A
 linux-backports-modules-2.6.38-10-generic N/A
 linux-firmware 1.52
RfKill:

SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 05/28/2011
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A05
dmi.board.name: 04VF8V
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 6
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA05:bd05/28/2011:svnDellInc.:pnOptiPlex790:pvr01:rvnDellInc.:rn04VF8V:rvrA00:cvnDellInc.:ct6:cvr:
dmi.product.name: OptiPlex 790
dmi.product.version: 01
dmi.sys.vendor: Dell Inc.