mais ton sources.list n´est pas très clair
le mien :
- lenny
deb http://ftp.fr.debian.org/debian/ lenny main contrib non-free
deb-src http://ftp.fr.debian.org/debian/ lenny main contrib non-free
- debian-marillat
deb http://www.debian-multimedia.org lenny main
deb-src http://www.debian-multimedia.org lenny main
- security
deb http://security.debian.org/ lenny/updates main contrib non-free
deb-src http://security.debian.org/ lenny/updates main contrib non-free
- autres
- vlc
deb
http://download.videolan.org/pub/videolan/debian/ sid main
- skype
deb http://download.skype.com/linux/repos/debian/ stable non-free
- opera
deb http://deb.opera.com/opera/ unstable non-free
- beryl
deb http://debian.beryl-project.org/ etch main
ban le mien n´est pas parfait non plus (pas de /etc/apt/preferences) mais il a l´air mieux, inspire toi en !