La cuestión es que me daba el mensaje que os he puesto en el título cuándo quería abrir el gestor de paquetes o cuándo intentaba (por que pensaba que podría instalar el Opera) instalar un programa.
La cuestión es que hice una gilipollez (un intento de arreglo). Sustituir el contenido de lectura y ahora me da otro tipo de error.
Ya sabeis, lo hice con un sudo gedit /etc/apt/sources.list en la consola. Por suerte guardé el contenido de dicho archivo y lo tengo en el escritorio.
Os lo dejo aquí:
Ese archivo lo sustituí por el contenido de este otro:# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://es.archive.ubuntu.com/ubuntu/ feisty main restricted
deb-src http://es.archive.ubuntu.com/ubuntu/ feisty main restricted
## Major bug fix updates produced after the final release of the
## distribution.
deb http://es.archive.ubuntu.com/ubuntu/ feisty-updates main restricted
deb-src http://es.archive.ubuntu.com/ubuntu/ feisty-updates main restricted
## 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
## WILL NOT receive any review or updates from the Ubuntu security
## team.
deb http://es.archive.ubuntu.com/ubuntu/ feisty
deb-src http://es.archive.ubuntu.com/ubuntu/ feisty
## 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://es.archive.ubuntu.com/ubuntu/ feisty multiverse
deb-src http://es.archive.ubuntu.com/ubuntu/ feisty 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://es.archive.ubuntu.com/ubuntu/ feisty-backports main restricted multiverse
# deb-src http://es.archive.ubuntu.com/ubuntu/ feisty-backports main restricted multiverse
deb http://security.ubuntu.com/ubuntu feisty-security main restricted
deb-src http://security.ubuntu.com/ubuntu feisty-security main restricted
deb http://security.ubuntu.com/ubuntu feisty-security
deb-src http://security.ubuntu.com/ubuntu feisty-security
deb http://security.ubuntu.com/ubuntu feisty-security multiverse
deb-src http://security.ubuntu.com/ubuntu feisty-security multiverse
De nada me sirvió. ¿Alguién sabe a que se debe el problema?.deb http://old-releases.ubuntu.com/ubuntu/ feisty-updates main restricted
deb-src http://old-releases.ubuntu.com/ubuntu/ feisty-updates main restricted
deb http://old-releases.ubuntu.com/ubuntu/ feisty universe
deb-src http://old-releases.ubuntu.com/ubuntu/ feisty universe
deb http://old-releases.ubuntu.com/ubuntu/ feisty multiverse
deb-src http://old-releases.ubuntu.com/ubuntu/ feisty multiverse
deb http://old-releases.ubuntu.com/ubuntu/ feisty-backports main restricted universe multiverse
deb-src http://old-releases.ubuntu.com/ubuntu/ feisty-backports main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ feisty-security main restricted
deb-src http://old-releases.ubuntu.com/ubuntu/ feisty-security main restricted
deb http://old-releases.ubuntu.com/ubuntu/ feisty-security universe
deb-src http://old-releases.ubuntu.com/ubuntu/ feisty-security universe
deb http://old-releases.ubuntu.com/ubuntu/ feisty-security multiverse
deb-src http://old-releases.ubuntu.com/ubuntu/ feisty-security multiverse
¿Por cierto, los archivos .deb no se instala sólo clickando?