package libpam-modules 1.1.3-2ubuntu2 failed to install/upgrade: ErrorMessage: './usr/share/man/man8/pam_shells.8.gz' is different from the same file on the system

Error while upgrading from xubuntu 11.04 to 11.10

ProblemType: Package
DistroRelease: Ubuntu 11.10
Package: libpam-modules 1.1.3-2ubuntu2
ProcVersionSignature: Ubuntu 2.6.38-12.51-generic 2.6.38.8
Uname: Linux 2.6.38-12-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 1.23-0ubuntu3
Architecture: amd64
Date: Sat Oct 15 22:43:20 2011
ErrorMessage: ErrorMessage: './usr/share/man/man8/pam_shells.8.gz' is different from the same file on the system
InstallationMedia: Xubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427)
SourcePackage: pam
Title: package libpam-modules 1.1.3-2ubuntu2 failed to install/upgrade: ErrorMessage: './usr/share/man/man8/pam_shells.8.gz' is different from the same file on the system
UpgradeStatus: Upgraded to oneiric on 2011-10-15 (0 days ago)