the problem had to do with the fact that, in the General page in Settings, i set the WordPress address to a different URL than the Blog address. the WP address was pointed at the root, and the blog address at root/wp (where my wordpress install is).
i guess what was happening was that everything happening in /wp was redirecting back to root, when then redirected to my blog homepage.
didn’t figure this out until i stumbled across those settings, changed them, and *totally* broke my site (couldn’t even login because of a redirect). just followed the phpmyadmin instructions in the link above to get things working.