update manager notify that cannot install ubuntu-desktop

[jencce]

steps:
1. sudo apt-get update check for updates
2. update-manager get out automaticlly
3. update-manager give a window says: cannot instal l ubuntu-destop, run ubuntu-bug update-manager ...etc
4. so i am here

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: update-manager 1:0.152.15
ProcVersionSignature: Ubuntu 3.0.0-9.14-generic 3.0.3
Uname: Linux 3.0.0-9-generic i686
Architecture: i386
Date: Fri Aug 26 09:02:29 2011
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=zh_CN:zh
 PATH=(custom, user)
 LANG=zh_CN.UTF-8
 SHELL=/bin/bash
SourcePackage: update-manager
UpgradeStatus: Upgraded to oneiric on 2011-08-26 (0 days ago)