package rsyslog 5.8.6-1ubuntu8.6 failed to install/upgrade: subprocess installed post-installation script returned error exit status 127

les mises à jour logicielles s'interrompe aprés leur téléchargement et pendant l'installation , l'installation ne s effectue jamais jusqu au bout

ProblemType: Package
DistroRelease: Ubuntu 12.04
Package: rsyslog 5.8.6-1ubuntu8.6
ProcVersionSignature: Ubuntu 3.2.0-57.87-generic 3.2.52
Uname: Linux 3.2.0-57-generic x86_64
NonfreeKernelModules: fglrx
ApportVersion: 2.0.1-0ubuntu17.6
Architecture: amd64
Date: Sat Jan 4 02:19:57 2014
DuplicateSignature: package:rsyslog:5.8.6-1ubuntu8.6:subprocess installed post-installation script returned error exit status 127
ErrorMessage: subprocess installed post-installation script returned error exit status 127
InstallationMedia: Ubuntu 12.04 "Precise" - Build amd64 LIVE Binary 20120425-15:28
MarkForUpload: True
SourcePackage: rsyslog
Title: package rsyslog 5.8.6-1ubuntu8.6 failed to install/upgrade: subprocess installed post-installation script returned error exit status 127
UpgradeStatus: No upgrade log present (probably fresh install)