Feed widget says feed is down.. it’s not..?

I’m running WordPress 2.0.4 and the latest Widgets plugin, and am having some issues with the RSS feed widget. Namely, it doesn’t work no matter what working feed I plug into it—and trying to search for the error message just brings up plenty of blogs with the same error (though probably for other reasons).

Any ideas here? Other sites on the same hosting account aggregate just fine, but this one’s giving me issues for some reason.