do-release-upgrade and update-manager crashes on migration from ubuntu precise to ubuntu quantal at migration evaluation

[François LEFÈVRE]

I have Ubuntu 12.04.01 Precise Pangolin for amd64
At boot, update-manager starts and show "Ubuntu 12.10 Quantal Quetzal is available. Start migration."
I start do-release-upgrade, but it crashed at "Evaluation of changes".
do-release-upgrade is closed, and update-manager starts.
It crashed at update check and show 1608 updates available, and crashes. It shows :
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Impossible d'installer certaines mises à jour

Exécutez une mise à niveau partielle pour installer autant de mises à jour que possible.
Ceci peut être dû à une mise à niveau précédente qui n'a pas été terminée.

--------------------------------- ------------
| Mise à niveau partielle | | Fermer |
--------------------------------- -------------
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I press the "partial migration" button, but the migration crashed and shows :
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Impossible d'évaluer la mise à niveau

Un problème irrémédiable est survenu lors de l'évaluation de la mise à niveau :
E:Impossible de corriger les problèmes, des paquets défectueux sont en mode "garder en l'état"

Cela peut-être du à un paquet logiciel non officiel, non fourni par Ubuntu.

Cela ressemble fort à un problème temporaire. Veuillez réessayer plus tard.
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ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: ubuntu-release-upgrader-core (not installed)
ProcVersionSignature: Ubuntu 3.5.0-10.10-generic 3.5.1
Uname: Linux 3.5.0-10-generic x86_64
ApportVersion: 2.0.1-0ubuntu14
Architecture: amd64
Date: Sat Oct 20 11:20:37 2012
InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Release amd64 (20101007)
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to precise on 2012-10-20 (0 days ago)

[Fabio Marconi (fabiomarconi)]

Thank you for taking the time to report this issue and helping to make Ubuntu better. Examining the information you have given us, this does not appear to be a bug report so we are closing it and converting it to a question in the support tracker. We understand the difficulties you are facing, but it is better to raise problems you are having in the support tracker at https://answers.launchpad.net/ubuntu if you are uncertain if they are bugs. You can also find help posting your problem in the support forum of your local Ubuntu's community http://loco.ubuntu.com/ or asking at http://askubuntu.com. For help on reporting bugs, see https://help.ubuntu.com/community/ReportingBugs.