irremediable error in update manager

[didier mouton]

System requests me to report the following bug of package "update-manager" joining this message:

'E:Encountered a section with no Package: header, E:Problem with MergeList /var/lib/apt/lists/mt.archive.ubuntu,com_ubuntu_dists_precise-backports_universe_i18n_Translation-en, E:Les listes de paquets ou le fichier "status" ne peuvent etre analyses ou lus'

Indeed, update-manager now fails at each attempt (since yesterday Sunday 09/09/2012). Restart did not cause any chamge. Alt+F12 (apport) failed to generate any report that I am aware of - I am not expert enough to use command line.
Software Center too fails to open.

Internet connection was extremely slow on 09/09/2012, webpages and content of emails would not load in Firefox/Thunderbird (no problem using other computer under ubuntu 11.10 oneiric - .in wifi, whille affected computer is wired to modem).

Not the first time mt.archive is causing trouble: weather applet had problems after update; had to be uninstalled, re-installed.

FYI: upgraded from oneiric to precise in July.
Hardware: Acer ER 1014, CPU AMD Athlon II Neo K325.
Please note that I changed to a new modem on 06/09 (Cisco model EPC3925, EuroDOCSIS 3.0) - worked perfectly out of the box.

Hope I was not mistaken in creating this bug report.
Many thx to Ubuntu teams and community.

[Ubuntu Foundations Team Bug Bot (crichton)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. Reviewing your bug report it seems that you are experiencing bug 346386. This issue happens when you have tried to update your package information when you are a network that didn't return the right files. This issue can be cleaned up by using the following commands in a terminal:

1.) sudo rm /var/lib/apt/lists/*
2.) sudo apt-get update

Thanks and good luck!

[This is an automated message. I apologize if it reached you inappropriately; please reopen the bug task if it was incorrect.]