do-release-upgrade crashed with AssertionError in confirmChanges()

[Andy]

Just trying to do an update via update manager

ProblemType: Crash
DistroRelease: Ubuntu 14.04
Package: ubuntu-release-upgrader-core 1:0.219.2
ProcVersionSignature: Ubuntu 3.13.0-20.42-generic 3.13.7
Uname: Linux 3.13.0-20-generic x86_64
ApportVersion: 2.14-0ubuntu1
Architecture: amd64
CrashDB: ubuntu
Date: Thu Apr 3 12:47:28 2014
ExecutablePath: /usr/bin/do-release-upgrade
InstallationDate: Installed on 2014-03-27 (6 days ago)
InstallationMedia: Xubuntu 14.04 LTS "Trusty Tahr" - Alpha amd64 (20140225)
InterpreterPath: /usr/bin/python3.4
PackageArchitecture: all
ProcCmdline: /usr/bin/python3 /usr/lib/ubuntu-release-upgrader/do-partial-upgrade --frontend=DistUpgradeViewGtk3
ProcEnviron:
 SHELL=/bin/bash
 LANG=en_US.UTF-8
 LANGUAGE=en_US
 PATH=(custom, no user)
PythonArgs: ['/usr/bin/do-release-upgrade', '--frontend=DistUpgradeViewGtk3']
SourcePackage: ubuntu-release-upgrader
Title: do-release-upgrade crashed with AssertionError in confirmChanges()
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups:

[Apport retracing service (apport)]

Thank you for taking the time to report this crash and helping to make this software better. This particular crash has already been reported and is a duplicate of bug #1294124, so is being marked as such. Please look at the other bug report to see if there is any missing information that you can provide, or to see if there is a workaround for the bug. Additionally, any further discussion regarding the bug should occur in the other report. Please continue to report any other bugs you may find.