The package downloads are currently running into trouble because of problems with getting the security updates (see:
http://www.us.debian.org/News/2005/20050920 and
http://www.us.debian.org/News/2005/20051004 ).
Here is a quote from the first news release:
“The recently released security update of XFree86 in DSA 816 for sarge and woody has caused the host security.debian.org to saturate its 100MBit/s network connection entirely. Due to the large number of X packages, the gross size of these packages and the high number of users who need to install the update, the server is busy sending out updates which exhaust its total outgoing bandwidth...”
By net installing almost any version of Debian right now with the security updates turned on, you are participating in a de facto denial-of-service attack on security.debian.org. You can try installing with the security updates turned off and then turn on the updates in the near future when the problem passes.
I have been fighting the same problem for the past two days installing Etch and just realized last night what was causing the problem.