não é conhecido na linha 1 na lista de fontes /etc/apt/sources.list.d/medibuntu.list E: A lista de fontes não pode ser lida.

Estou com esse problema. Estou consultado vários sites e fazendo  várias tentativas para resolver o problema.

Tudo aconteceu quando baixei vários codecs para fazer um tutorial sobre o aplicativo gráfico BLENDER 3D usando a técnica SCREENCAST (Gravação de tela do computador).
O arquivo gerado no meu PC com a extesão .mp4 não abre para assistir no PC. Resolvi enviar para o youtube assim mesmo e no youtube abre tranquilo. Eu baixei varios codecs para abertura de vídeo e tem alguma coisa que está sendo instalada no linux. Quando vou fechar aparece a mensagem: "Ainda há um processo sendo executado neste terminal. Fechar este terminal irá matá-lo". Tá aberto desde ontem à tarde. Se alguém tiver alguma sugestão do que pode ser. 

Tentei este comando: Abra o Terminal com CTRL + ALT + T
Copie e cole este comando no Terminal.
cat /etc/apt/sources.list

Aparece esta lista.

 deb cdrom:[Ubuntu 9.04 _Jaunty Jackalope_ - Release i386 (20090420.1)]/ jaunty 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/ jaunty main restricted universe
deb-src http://br.archive.ubuntu.com/ubuntu/ jaunty restricted main universe #Added by software-properties

## Major bug fix updates produced after the final release of the
## distribution.

## 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.

## 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.

## 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/ jaunty-backports main restricted universe multiverse
# deb-src http://br.archive.ubuntu.com/ubuntu/ jaunty-backports main restricted universe 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://security.ubuntu.com/ubuntu/ jaunty-security restricted main universe
deb-src http://br.archive.ubuntu.com/ubuntu/ jaunty-security restricted main universe
deb http://br.archive.ubuntu.com/ubuntu/ jaunty-updates restricted main universe
deb-src http://br.archive.ubuntu.com/ubuntu/ jaunty-updates restricted main universe
deb http://archive.canonical.com/ubuntu jaunty partner
deb-src http://archive.canonical.com/ubuntu jaunty partner
deb http://security.ubuntu.com/ubuntu/ jaunty-security restricted main universe

O prolema continua

Vou tentar estes comando agora:
sudo rm /etc/apt/sources.list.d/medibuntu.list
sudo apt-get update
sudo apt-get upgrade

Em parte resolveu. Agora aceita digitar comandos.
Mas quando vou atualizar pelo atualizador aparece a tela abaixo:

Consultas:
https://www.vivaolinux.com.br/topico/Desktops/Poderiam-me-ajudar
https://www.vivaolinux.com.br/topico/vivaolinux/Erro-ao-instalar-programas-e-ao-fazer-o-update