Problema con repositorios backport

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Hola lista,

me imagino que esto le habrá pasado a más gente, pero rebuscando no he
encontrado solución en el histórico de la lista.

Resulta que al utilizar apt (vía synaptic) tengo problemas con los
repositorios  de los backports. He probado varios y:

Los de caliu:

tp://ftp2.caliu.info/backports/dists/hoary-backports/main/binary-i386/Packages.gz:
Imposible traer archivo, el servidor dijo 'Failed to open file.  '
ftp://ftp2.caliu.info/backports/dists/hoary-backports/universe/binary-i386/Packages.gz:
Imposible traer archivo, el servidor dijo 'Failed to open file.  '
ftp://ftp2.caliu.info/backports/dists/hoary-backports/multiverse/binary-i386/Packages.gz:
Imposible traer archivo, el servidor dijo 'Failed to open file.  '
ftp://ftp2.caliu.info/backports/dists/hoary-backports/restricted/binary-i386/Packages.gz:
Imposible traer archivo, el servidor dijo 'Failed to open file.  '

Los de planetmirror:

http://public.planetmirror.com/pub/ubuntu-backports/dists/hoary-extras/deb/binary-i386/Packages.gz:
404 Not Found [IP: 203.16.234.19 80]
http://public.planetmirror.com/pub/ubuntu-backports/dists/hoary-backports/main/binary-i386/Packages.gz:
404 Not Found [IP: 203.16.234.19 80]
http://public.planetmirror.com/pub/ubuntu-backports/dists/hoary-backports/universe/binary-i386/Packages.gz:
404 Not Found [IP: 203.16.234.19 80]
http://public.planetmirror.com/pub/ubuntu-backports/dists/hoary-backports/multiverse/binary-i386/Packages.gz:
404 Not Found [IP: 203.16.234.19 80]
http://public.planetmirror.com/pub/ubuntu-backports/dists/hoary-backports/restricted/binary-i386/Packages.gz:
404 Not Found [IP: 203.16.234.19 80]
http://public.planetmirror.com/pub/ubuntu-backports/dists/hoary-backports/deb/binary-i386/Packages.gz:
404 Not Found [IP: 203.16.234.19 80]
http://public.planetmirror.com/pub/ubuntu-backports/hoary-extras-staging/dists/main/universe/binary-i386/Packages.gz:
404 Not Found [IP: 203.16.234.19 80]
http://public.planetmirror.com/pub/ubuntu-backports/hoary-extras-staging/dists/main/multiverse/binary-i386/Packages.gz:
404 Not Found [IP: 203.16.234.19 80]
http://public.planetmirror.com/pub/ubuntu-backports/hoary-extras-staging/dists/main/restricted/binary-i386/Packages.gz:
404 Not Found [IP: 203.16.234.19 80]
http://public.planetmirror.com/pub/ubuntu-backports/hoary-extras-staging/dists/main/deb/binary-i386/Packages.gz:
404 Not Found [IP: 203.16.234.19 80]
http://public.planetmirror.com/pub/ubuntu-backports/hoary-backports-staging/dists/main/universe/binary-i386/Packages.gz:
404 Not Found [IP: 203.16.234.19 80]
http://public.planetmirror.com/pub/ubuntu-backports/hoary-backports-staging/dists/main/multiverse/binary-i386/Packages.gz:
404 Not Found [IP: 203.16.234.19 80]
http://public.planetmirror.com/pub/ubuntu-backports/hoary-backports-staging/dists/main/restricted/binary-i386/Packages.gz:
404 Not Found [IP: 203.16.234.19 80]

Sobre todo quiero actualizar el firefox, que ahora ni se me abre...

Un saludo y gracias por la ayuda.