dbus package fails to upgrade because "messagebus" user already exists

[sas]

Binary package hint: dbus

Release: Ubuntu 10.04.1 LTS 64 bit

Package: dbus 1.2.16-2ubuntu4.1 amd64

What happened: Update manager came up with important security updates: dbus, dbus-x11, libdus-1-3. Installation failed, log is pasted below:

(Reading database ... 284653 files and directories currently installed.)
Preparing to replace libdbus-1-3 1.2.16-2ubuntu4 (using .../libdbus-1-3_1.2.16-2ubuntu4.1_amd64.deb) ...
Unpacking replacement libdbus-1-3 ...
Preparing to replace dbus 1.2.16-2ubuntu4 (using .../dbus_1.2.16-2ubuntu4.1_amd64.deb) ...
Unpacking replacement dbus ...
Preparing to replace dbus-x11 1.2.16-2ubuntu4 (using .../dbus-x11_1.2.16-2ubuntu4.1_amd64.deb) ...
Unpacking replacement dbus-x11 ...
Processing triggers for man-db ...
Processing triggers for ureadahead ...
Setting up libdbus-1-3 (1.2.16-2ubuntu4.1) ...

Setting up dbus (1.2.16-2ubuntu4.1) ...
The system user `messagebus' already exists. Exiting.
Error org.freedesktop.DBus.Error.NoReply: Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.
dpkg: error processing dbus (--configure):
 subprocess installed post-installation script returned error exit status 1
dpkg: dependency problems prevent configuration of dbus-x11:
 dbus-x11 depends on dbus; however:
  Package dbus is not configured yet.
dpkg: error processing dbus-x11 (--configure):
 dependency problems - leaving unconfigured
Processing triggers for libc-bin ...
ldconfig deferred processing now taking place
No apport report written because the error message indicates it's a follow-up error from a previous failure.
                            Errors were encountered while processing:
 dbus
 dbus-x11
E: Sub-process /usr/bin/dpkg returned an error code (1)
A package failed to install. Trying to recover:
Setting up dbus (1.2.16-2ubuntu4.1) ...
The system user `messagebus' already exists. Exiting.

ProblemType: Package
DistroRelease: Ubuntu 10.04
Package: dbus 1.2.16-2ubuntu4.1
ProcVersionSignature: Ubuntu 2.6.32-27.49-generic 2.6.32.26+drm33.12
Uname: Linux 2.6.32-27-generic x86_64
NonfreeKernelModules: nvidia
Architecture: amd64
Date: Wed Jan 19 09:54:10 2011
ErrorMessage: subprocess installed post-installation script returned error exit status 1
InstallationMedia: Ubuntu 9.10 "Karmic Koala" - Release amd64 (20091027)
SourcePackage: dbus
Title: package dbus 1.2.16-2ubuntu4.1 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Hartmut Kabus (kabus-saturn)]

dbus gets installed again if you temporarily delete user "messagebus" out of "/etc/passwd"; but new "messagebus" gets a different UID. To repair the system you should synchronize the UIDs over all the filesystem.
It would be the better way to patch the configure-script of package dbus to not add a new user in case of update (add only on new installation) or to ignore the error return of useradd in case of pe-existence of the user to add!