do-release-upgrade fails upgrading 12.04 to 14.04

[Simon Bazley]

not sure what I can add to be helpful, I ran do-release-upgrade to upgrade an old machine from 12.04 to 14.04 and it first told me it would disable all 3rd party add-ons (and prompts to recover or close the window)

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: update-manager 1:0.156.14.17
ProcVersionSignature: Ubuntu 3.2.0-72.107-generic 3.2.64
Uname: Linux 3.2.0-72-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.0.1-0ubuntu17.8
Architecture: amd64
Date: Wed Nov 26 20:45:43 2014
GsettingsChanges:

InstallationMedia: Ubuntu-Server 12.04.1 LTS "Precise Pangolin" - Release amd64 (20120817.3)
MarkForUpload: True
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=en_GB:en
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
SourcePackage: update-manager
Symptom: ubuntu-release-upgrader-core
UpgradeStatus: Upgraded to precise on 2014-11-26 (0 days ago)