I would say the mirror was down, you are not the first reporting this. You can also change the Debian mirror if this one is too slow. This list should help you:http://www.debian.org/mirror/list.en.htmlhttp://http.debian.net/debian, this one, seems really to be a betch.
netselect-apt automatically creates a sources.list file for using with apt for the specified distribution by downloading the list of Debian mirrors using wget and choosing the fastest servers (both US and non-US) using netselect.
I've inherited a system (Debian Squeeze) that has a Debian mirror set up within it, which is something I have basically no experience with. The problem with it is, it has completely filled up it's partition.