If you use Miranda and have been wondering why you haven't been receiving messages from your AIM contacts (or maybe you haven't been wondering because you didn't notice), it's because AOL changed the protocol. You need to update Miranda. If you're using a development build, you'll need to grab the AIM plugin from the 0.6.3 release.
For some reason I had to go digging to find this out. It's not mentioned on the front page of Miranda's website, which just has a generic "Miranda IM v0.6.3 Released" blurb that doesn't mention the AIM fix unless you click through. Argh.
If you've been sending me messages on AIM recently and have been wondering why I've been ignoring you, this is why.