ayda Línea 16 mal formada en la lista de fuentes

#deb cdrom:[Ubuntu 12.04 LTS _Precise Pangolin_ - Release i386 (20120423)]/ precise main restricted

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

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

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. 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/ precise
#deb-src http://es.archive.ubuntu.com/ubuntu/ precise
##deb http://es.archive.ubuntu.com/ubuntu/ precise-updates
#deb-src http://es.archive.ubuntu.com/ubuntu/ precise-updates
#
## 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/ precise multiverse
deb-src http://es.archive.ubuntu.com/ubuntu/ precise multiverse
deb http://es.archive.ubuntu.com/ubuntu/ precise-updates multiverse
deb-src http://es.archive.ubuntu.com/ubuntu/ precise-updates multiverse

## 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://security.ubuntu.com/ubuntu precise-security main restricted
deb-src http://security.ubuntu.com/ubuntu precise-security main restricted
deb http://security.ubuntu.com/ubuntu precise-security
deb-src http://security.ubuntu.com/ubuntu precise-security
deb http://security.ubuntu.com/ubuntu precise-security multiverse
deb-src http://security.ubuntu.com/ubuntu precise-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 precise partner
deb-src http://archive.canonical.com/ubuntu precise 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 precise main
deb http://es.archive.ubuntu.com/ubuntu/ precise-proposed restricted main multiverse
deb-src http://extras.ubuntu.com/ubuntu precise main
deb http://es.archive.ubuntu.com/ubuntu/ precise-backports restricted main multiverse
deb http://archive.canonical.com/ubuntu/ lucid partner
deb-src http://archive.canonical.com/ubuntu/ lucid partner

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puedes comentar las dos ultimas que son de lucid, agregando ## al inicio, lo guardas y ejecutas en la consola un update:
sudo apt-get update
y mira si te arroja un error.

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