upgrade from 12.04 to 14.04 crashes

During the upgrade from 12.04 to 14.04.01 this message appeared:

An unresolvable problem occurred while calculating the upgrade.

 This can be caused by:
 * Upgrading to a pre-release version of Ubuntu
 * Running the current pre-release version of Ubuntu
 * Unofficial software packages not provided by Ubuntu

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: update-manager 1:0.156.14.17
ProcVersionSignature: Ubuntu 3.2.0-69.103-generic 3.2.62
Uname: Linux 3.2.0-69-generic i686
ApportVersion: 2.0.1-0ubuntu17.7
Architecture: i386
Date: Wed Oct 15 20:52:56 2014
GsettingsChanges:
 com.ubuntu.update-manager first-run false
 com.ubuntu.update-manager launch-time 1413398414
 com.ubuntu.update-manager window-height 500
 com.ubuntu.update-manager window-width 600
InstallationMedia: Ubuntu-Studio 10.04 LTS "Lucid Lynx" - Release i386 (20100427.1)
MarkForUpload: True
PackageArchitecture: all
SourcePackage: update-manager
Symptom: ubuntu-release-upgrader-core
UpgradeStatus: Upgraded to precise on 2014-10-15 (0 days ago)
VarLogDistupgradeTermlog: