Well, it seems to be the case that a plugin that had been recommended to me (Bad Behavior) seems to have been blocking some legitimate traffic to the site. I only had it installed to cut down on spam, and now I have a new system that does a much better job of that; so… I’ve disabled it.
If any of you were having trouble with rss feeds or the like, this should be fixed now :\
Sorry for any inconvenience this may have caused (not sorry to the spammers though :P)