Ошибка выборки репозитория

Вот ошибки, которые я получаю:

(как вы видите, я подключаюсь к Интернету через доверенность департамента образования)

W:Failed to fetch http://au.archive.ubuntu.com/ubuntu/dists/quantal/Release.gpg  Something wicked happened resolving 'educf.proxy.tas.edu.au:8080' (-5 - No address associated with hostname)
W:Failed to fetch http://extras.ubuntu.com/ubuntu/dists/quantal/Release.gpg  Something wicked happened resolving 'educf.proxy.tas.edu.au:8080' (-5 - No address associated with hostname)

[CUT OUT SOME RESULTS, TOO MANY LINKS]

E:Some index files failed to download. They have been ignored, or old ones used instead.