Jochen Spieker wrote:
Very strange. Did you try changing to another mirror, just to see if
that helps? Did you set a proxy in /etc/apt/apt.conf{,.d}?
That was the problem: we had previously been using the approx proxy server, and there was an Acquire::http::proxy set in /etc/apt/apt.conf.d. During the upgrade to wheezy, approx was held back for some reason and wasn't functioning, so I switched back to http://ftp.us.debian.org/debian/, but the file was preventing it from working.
Commenting out the proxy in /etc/apt/apt.conf.d/70debconf fixed the problem. (Then I was able to upgrade approx and switch back to using the proxy, which is for a cluster setup, as before.)
Thanks so much for your help! --SGJ