Problèmes avec les DNS et la mise à jour de Debian

J'ai essayé de mettre à jour mon serveur debian dreamplug avec la commande exécutée en tant que root apt-get update et j'ai reçu ces erreurs.

Err http://security.debian.org lenny/updates Release.gpg                                                                                     
  Could not resolve 'security.debian.org'
Err http://security.debian.org lenny/updates/main Translation-en_US                                                                          
  Could not resolve 'security.debian.org'
Err http://security.debian.org lenny/updates/contrib Translation-en_US                                                                       
  Could not resolve 'security.debian.org'
Err http://security.debian.org lenny/updates/non-free Translation-en_US                                                                      
  Could not resolve 'security.debian.org'
Err http://www.backports.org lenny-backports Releasegpg                                                                                     
  Could not resolve 'www.backports.org'
Err http://www.backports.org lenny-backports/main Translation-en_US                                      
  Could not resolve 'www.backports.org'
Err http://www.backports.org lenny-backports/contrib Translation-en_US                                   
  Could not resolve 'www.backports.org'
Err http://www.backports.org lenny-backports/non-free Translation-en_US                                  
  Could not resolve 'www.backports.org'
Err http://ftp.us.debian.org lenny Release.gpg                                                           
  Could not resolve 'ftp.us.debian.org'
Err http://ftp.us.debian.org lenny/main Translation-en_US              
  Could not resolve 'ftp.us.debian.org'
Err http://ftp.us.debian.org lenny/contrib Translation-en_US           
  Could not resolve 'ftp.us.debian.org'
Err http://ftp.us.debian.org lenny/non-free Translation-en_US          
  Could not resolve 'ftp.us.debian.org'
Err http://http.us.debian.org stable Release.gpg                       
  Could not resolve 'http.us.debian.org'
Err http://http.us.debian.org stable/main Translation-en_US            
  Could not resolve 'http.us.debian.org'
Err http://http.us.debian.org stable/contrib Translation-en_US         
  Could not resolve 'http.us.debian.org'
Err http://http.us.debian.org stable/non-free Translation-en_US        
  Could not resolve 'http.us.debian.org'
Reading package lists... Done                                          
W: Failed to fetch http://ftp.us.debian.org/debian/dists/lenny/Release.gpg  Could not resolve 'ftp.us.debian.org'

W: Failed to fetch http://ftp.us.debian.org/debian/dists/lenny/main/i18n/Translation-en_US.gz  Could not resolve 'ftp.us.debian.org'

W: Failed to fetch http://ftp.us.debian.org/debian/dists/lenny/contrib/i18n/Translation-en_US.gz  Could not resolve 'ftp.us.debian.org'

W: Failed to fetch http://ftp.us.debian.org/debian/dists/lenny/non-free/i18n/Translation-en_US.gz  Could not resolve 'ftp.us.debian.org'

W: Failed to fetch http://http.us.debian.org/debian/dists/stable/Release.gpg  Could not resolve 'http.us.debian.org'

W: Failed to fetch http://http.us.debian.org/debian/dists/stable/main/i18n/Translation-en_US.gz  Could not resolve 'http.us.debian.org'

W: Failed to fetch http://http.us.debian.org/debian/dists/stable/contrib/i18n/Translation-en_US.gz  Could not resolve 'http.us.debian.org'

W: Failed to fetch http://http.us.debian.org/debian/dists/stable/non-free/i18n/Translation-en_US.gz  Could not resolve 'http.us.debian.org'

W: Failed to fetch http://security.debian.org/dists/lenny/updates/Release.gpg  Could not resolve 'security.debian.org'

W: Failed to fetch http://security.debian.org/dists/lenny/updates/main/i18n/Translation-en_US.gz  Could not resolve 'security.debian.org'

W: Failed to fetch http://security.debian.org/dists/lenny/updates/contrib/i18n/Translation-en_US.gz  Could not resolve 'security.debian.org'

W: Failed to fetch http://security.debian.org/dists/lenny/updates/non-free/i18n/Translation-en_US.gz  Could not resolve 'security.debian.org'

W: Failed to fetch http://www.backports.org/debian/dists/lenny-backports/Release.gpg  Could not resolve 'www.backports.org'

W: Failed to fetch http://www.backports.org/debian/dists/lenny-backports/main/i18n/Translation-en_US.gz  Could not resolve 'www.backports.org'

W: Failed to fetch http://www.backports.org/debian/dists/lenny-backports/contrib/i18n/Translation-en_US.gz  Could not resolve 'www.backports.org'

W: Failed to fetch http://www.backports.org/debian/dists/lenny-backports/non-free/i18n/Translation-en_US.gz  Could not resolve 'www.backports.org'

W: Some index files failed to download, they have been ignored, or old ones used instead.
W: You may want to run apt-get update to correct these problems

Je suis capable d'envoyer des ping aux adresses IP mais pas aux espaces de noms. Je ne parviens pas à comprendre le problème. Mon fichier /etc/resolv.conf contient serveur de noms 192.168.1.2 qui est mon routeur.