Fiz o update utilizando essa source.list e alguns erros aconteceram...
SOURCE.LIST## Add comments (##) in front of any line to remove it from being checked.
## Use the following sources.list at your own risk.
deb http://archive.ubuntu.com/ubuntu dapper main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu dapper main restricted universe multiverse
## MAJOR BUG FIX UPDATES produced after the final release
deb http://archive.ubuntu.com/ubuntu dapper-updates main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu dapper-updates main restricted universe multiverse
## UBUNTU SECURITY UPDATES
deb http://security.ubuntu.com/ubuntu dapper-security main restricted universe multiverse
deb-src http://security.ubuntu.com/ubuntu dapper-security main restricted universe multiverse
## BACKPORTS REPOSITORY (Unsupported. May contain illegal packages. Use at own risk.)
deb http://archive.ubuntu.com/ubuntu dapper-backports main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu dapper-backports main restricted universe multiverse
## PLF REPOSITORY (Unsupported. May contain illegal packages. Use at own risk.)
deb http://packages.freecontrib.org/plf dapper free non-free
deb-src http://packages.freecontrib.org/plf dapper free non-free
ERROSgzip: stdin: not in gzip format
Err http://archive.ubuntu.com dapper/universe Sources
Sub-processo gzip retornou um código de erro (1)
84% [37 Packages gzip 0] 28,9kB/s 34s
gzip: stdin: not in gzip format
Err http://archive.ubuntu.com dapper-backports/main Packages
Sub-processo gzip retornou um código de erro (1)
Baixados 5022kB em 17m8s (4881B/s)
Falha ao baixar http://packages.freecontrib.org/plf/dists/dapper/Release.gpg Falaha temporária resolvendo 'packages.freecontrib.org'
Falha ao baixar http://archive.ubuntu.com/ubuntu/dists/dapper/universe/source/Sources.gz Sub-processo gzip retornou um código de erro (1)
Falha ao baixar http://archive.ubuntu.com/ubuntu/dists/dapper-backports/main/binary-i386/Packages.gz Sub-processo gzip retornou um código de erro (1)
Lendo Lista de Pacotes... Pronto
W: Alguns arquivos de índice falharam no download, eles foram ignorados ou os antigos foram usados em seu lugar.
Quando fui abrir o menu vários ícones desapareceram....Usuários e Grupos, Gerenciador de pacotes e outros...
Alguem sabe o que aconteceu?