Ma logithèque UBUNTU ne fonctionne plus

Voici ce qui s'inscrit quand je copie colle la commande :

charlotte@Charlotte:~$ cat /etc/apt/sources.list
# medibuntu
deb http://fr.packages.medibuntu.org/ lucid free non-free

# deb cdrom:[Ubuntu 11.04 _Natty Narwhal_ - Release i386 (20110427.1)]/ natty main restricted
wget -q http://packages.medibuntu.org/medibuntu-key.gpg -O- | sudo apt-key add -
$ sudo aptitude update
$ sudo aptitude install libdvdcss2


# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://fr.archive.ubuntu.com/ubuntu/ natty main restricted
deb-src http://fr.archive.ubuntu.com/ubuntu/ natty main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://fr.archive.ubuntu.com/ubuntu/ natty-updates main restricted
deb-src http://fr.archive.ubuntu.com/ubuntu/ natty-updates main restricted

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://fr.archive.ubuntu.com/ubuntu/ natty universe
deb-src http://fr.archive.ubuntu.com/ubuntu/ natty universe
deb http://fr.archive.ubuntu.com/ubuntu/ natty-updates universe
deb-src http://fr.archive.ubuntu.com/ubuntu/ natty-updates universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://fr.archive.ubuntu.com/ubuntu/ natty multiverse
deb-src http://fr.archive.ubuntu.com/ubuntu/ natty multiverse
deb http://fr.archive.ubuntu.com/ubuntu/ natty-updates multiverse
deb-src http://fr.archive.ubuntu.com/ubuntu/ natty-updates multiverse

## Uncomment the following two lines to add software from the 'backports'
## repository.
## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
# deb http://fr.archive.ubuntu.com/ubuntu/ natty-backports main restricted universe multiverse
# deb-src http://fr.archive.ubuntu.com/ubuntu/ natty-backports main restricted universe multiverse

deb http://security.ubuntu.com/ubuntu natty-security main restricted
deb-src http://security.ubuntu.com/ubuntu natty-security main restricted
deb http://security.ubuntu.com/ubuntu natty-security universe
deb-src http://security.ubuntu.com/ubuntu natty-security universe
deb http://security.ubuntu.com/ubuntu natty-security multiverse
deb-src http://security.ubuntu.com/ubuntu natty-security multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
deb http://archive.canonical.com/ubuntu natty partner
# deb-src http://archive.canonical.com/ubuntu natty partner

## This software is not part of Ubuntu, but is offered by third-party
## developers who want to ship their latest software.
deb http://extras.ubuntu.com/ubuntu natty main
deb-src http://extras.ubuntu.com/ubuntu natty main
charlotte@Charlotte:~$ cat /etc/lsb-release


Une idée de ce que je peux faire pour réparer le problème ?

Merci pour ton aide !