impossible de mettre à jour la nouvelle version

[laurent]

Ubuntu 12.04 Impossible d'évaluer la mise à niveau vers upgrade

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

Si rien de tout cela ne s'applique, veuillez signaler ce bogue en utilisant la commande 'ubuntu-bug ubuntu-release-upgrader-core' dans un terminal.

Thanks for your help

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: Mon Sep 29 21:03:38 2014
GsettingsChanges:
 com.ubuntu.update-manager first-run false
 com.ubuntu.update-manager launch-time 1412016481
 com.ubuntu.update-manager show-details true
 com.ubuntu.update-manager window-height 570
 com.ubuntu.update-manager window-width 600
InstallationMedia: Ubuntu 9.10 "Karmic Koala" - Release i386 (20091028.5)
MarkForUpload: True
PackageArchitecture: all
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=fr_CH.UTF-8
 SHELL=/bin/bash
SourcePackage: update-manager
Symptom: ubuntu-release-upgrader-core
UpgradeStatus: Upgraded to precise on 2014-09-29 (0 days ago)
VarLogDistupgradeTermlog: