Não consigo atualizar o ubuntu 11.04

[nlsouza]

Estou com o problema abaixo, alguem poderia me ajudar? Obrigado a todos.

E: Impossível analisar arquivo de pacote /var/lib/apt/lists/br.archive.ubuntu.com_ubuntu_dists_natty_main_i18n_Translation-pt%5fBR (1)
E: A lista de pacotes ou o arquivo de estado não puderam ser analisados ou abertos.
E: _cache->open() failed, please report.

Meu source.list esta desta forma:

# deb cdrom:[Ubuntu 11.04 _Natty Narwhal_ - Release i386 (20110427.1)]/ natty main restricted

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

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

[Andreson Goveia]

http://ubuntuforum-br.org/index.php/topic,82181.msg454771.html#msg454771

[nlsouza]

Como faço para mudar este servidor?

[Andreson Goveia]

Como faço para mudar este servidor?

Synaptic -> Repositório