update-manager crashon password prompt cancel

[Robert Roth]

Binary package hint: update-manager

Steps to reproduce:
1. Start update-manager
2. Click install updates
3. Cancel the password prompt

Expected result :
The update manager is fully functional, you can deselect some packages, then click install updates ...
What happens instead:
Update manager crashes with :

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/defer/__init__.py", line 472, in _inline_callbacks
    result = gen.throw(result.type, result.value, result.traceback)
  File "/usr/lib/python2.7/dist-packages/aptdaemon/gtkwidgets.py", line 633, in _run
    yield self._transaction.run()
aptdaemon.errors.NotAuthorizedError: org.freedesktop.PolicyKit.Error.NotAuthorized: ('system-bus-name', {'name': ':1.47'}): org.debian.apt.upgrade-packages

ProblemType: Crash
DistroRelease: Ubuntu 11.04
Package: update-manager 1:0.146.5
ProcVersionSignature: Ubuntu 2.6.38-7.39-generic-pae 2.6.38
Uname: Linux 2.6.38-7-generic-pae i686
Architecture: i386
Date: Tue Mar 29 19:13:58 2011
ExecutablePath: /usr/bin/update-manager
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Alpha i386 (20110202)
InterpreterPath: /usr/bin/python2.7
ProcCmdline: /usr/bin/python2.7 /usr/bin/update-manager
ProcEnviron:
 SHELL=/bin/bash
 LANG=en_US.UTF-8
 LANGUAGE=en_US:en
PythonArgs: ['/usr/bin/update-manager']
SourcePackage: update-manager
Title: update-manager crashed with NotAuthorizedError in _run(): org.freedesktop.PolicyKit.Error.NotAuthorized: ('system-bus-name', {'name': ':1.47'}): org.debian.apt.upgrade-packages
UpgradeStatus: Upgraded to natty on 2011-03-28 (0 days ago)
UserGroups: adm admin cdrom dialout libvirtd lpadmin plugdev sambashare