Missing group in contact list

[SS3 GokouX]

I went to re-sort my contacts, so I unhid the offline peoples, moved some people around, deleted a couple people, and deleted an empty group (probably from one of my other accounts that I rarely use). I then re-hid the offline contacts. Just a few minutes ago I noticed my list was extremely short: one of my groups has gone missing. If I show offline contacts, the missing group reappears, along with the online and offline users it contains.

And, I don't know if it's just my machine lagging a little (ancient 400 mhz G4 that gets put to shame by my G5...), but when I hide offline contacts, the group header for the missing group appears for a moment and then disappears (the triangle is pointing down but no contacts are displayed).

I'm running the .75 beta, using AIM (only one account is signed on). Closing the window and bringing it back doesn't fix it, neither does disconnecting and re-connecting. I've just quit and reopened Adium and it's back to normal now.

My only guess is that editing (re-sorting and deleting contacts/groups) must have triggered it. But what do I know, could be something else completely.