Copiaci questo (ho solo decommentato il tuo vecchio, vediamo se da problemi)

codice:
deb cdrom:[Kubuntu 7.10 _Gutsy Gibbon_ - Release amd64 (20071016.1)]/ gutsy main restricted
 # See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
 # newer versions of the distribution.
 
deb http://it.archive.ubuntu.com/ubuntu/ gutsy main restricted
deb-src http://it.archive.ubuntu.com/ubuntu/ gutsy main restricted
 
 ## Major bug fix updates produced after the final release of the
 ## distribution.
deb http://it.archive.ubuntu.com/ubuntu/ gutsy-updates main restricted
deb-src http://it.archive.ubuntu.com/ubuntu/ gutsy-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
 ## universe WILL NOT receive any review or updates from the Ubuntu security
 ## team.
deb http://it.archive.ubuntu.com/ubuntu/ gutsy universe
deb-src http://it.archive.ubuntu.com/ubuntu/ gutsy universe
deb http://it.archive.ubuntu.com/ubuntu/ gutsy-updates universe
deb-src http://it.archive.ubuntu.com/ubuntu/ gutsy-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://it.archive.ubuntu.com/ubuntu/ gutsy multiverse
 deb-src http://it.archive.ubuntu.com/ubuntu/ gutsy multiverse
 deb http://it.archive.ubuntu.com/ubuntu/ gutsy-updates multiverse
 deb-src http://it.archive.ubuntu.com/ubuntu/ gutsy-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://it.archive.ubuntu.com/ubuntu/ gutsy-backports main restricted universe multiverse
 deb-src http://it.archive.ubuntu.com/ubuntu/ gutsy-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://archive.canonical.com/ubuntu gutsy partner
 deb-src http://archive.canonical.com/ubuntu gutsy partner
 
 deb http://security.ubuntu.com/ubuntu gutsy-security main restricted
 deb-src http://security.ubuntu.com/ubuntu gutsy-security main restricted
 deb http://security.ubuntu.com/ubuntu gutsy-security universe
 deb-src http://security.ubuntu.com/ubuntu gutsy-security universe
 deb http://security.ubuntu.com/ubuntu gutsy-security multiverse
 deb http://archive.ubuntu.com/ubuntu/ gutsy main universe restricted
 deb-src http://security.ubuntu.com/ubuntu gutsy-security multiverse
dai sudo apt-get update, e vediamo come va