Teste isso:
Ligue o seu computador.
Pressione e segure a tecla Shift, o que abrirá o menu do Grub.
Selecione a linha que começa com ---- Advanced options
.
Selecione a linha que termina com ---- (recovery mode)
.
Seu pc deve exibir um menu com várias opções.
Selecione a linha ---- Drop to root shell prompt
.
No terminal, execute:
mount -o remount,rw /
mount --all
nano /etc/apt/sources.list
No arquivo aberto.
Exclua o conteúdo.
Cole o seguinte:
deb http://us.archive.ubuntu.com/ubuntu/ precise main restricted
# deb-src http://us.archive.ubuntu.com/ubuntu/ precise main restricted
deb http://us.archive.ubuntu.com/ubuntu/ precise-updates main restricted
# deb-src http://us.archive.ubuntu.com/ubuntu/ precise-updates main restricted
deb http://us.archive.ubuntu.com/ubuntu/ precise universe
# deb-src http://us.archive.ubuntu.com/ubuntu/ precise universe
deb http://us.archive.ubuntu.com/ubuntu/ precise-updates universe
# deb-src http://us.archive.ubuntu.com/ubuntu/ precise-updates universe
deb http://us.archive.ubuntu.com/ubuntu/ precise multiverse
# deb-src http://us.archive.ubuntu.com/ubuntu/ precise multiverse
deb http://us.archive.ubuntu.com/ubuntu/ precise-updates multiverse
# deb-src http://us.archive.ubuntu.com/ubuntu/ precise-updates multiverse
deb http://us.archive.ubuntu.com/ubuntu/ precise-backports main restricted universe multiverse
# deb-src http://us.archive.ubuntu.com/ubuntu/ precise-backports main restricted universe multiverse
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 universe
# deb-src http://security.ubuntu.com/ubuntu precise-security universe
deb http://security.ubuntu.com/ubuntu precise-security multiverse
# deb-src http://security.ubuntu.com/ubuntu precise-security multiverse
deb http://archive.canonical.com/ubuntu precise partner
# deb-src http://archive.canonical.com/ubuntu precise partner
deb http://extras.ubuntu.com/ubuntu precise main
# deb-src http://extras.ubuntu.com/ubuntu precise main
deb http://us.archive.ubuntu.com/ubuntu/ precise-proposed universe multiverse restricted main
Ctrl + U , cole o texto. Ctrl + O , salve o arquivo. Ctrl + X , perto do nano.
Continue em execução:
apt-get update
apt-get dist-upgrade
apt-get -f install
dpkg --configure -a
apt-get install --reinstall ubuntu-desktop
apt-get autoremove
apt-get clean
reboot