So I wasn't getting any group chat invitations in Trillian, so I reinstalled it. This forced me to re-rename all the people on my contact list, but at least I get invites again.
Anyhow, a buddy of mine wouldn't keep his new name. I replaced his AIM screen name with his first and last name, it'd be fine, and then I'd restart. And it was back to what it was.
Everybody else changed fine, but not this guy. And I remembered having this problem with him before.
I opened up the buddies.xml file and fixed his name directly, and it finally worked. I still don't know why his name wasn't ever updating like everyone else's, but at least I don't have to look at a screen name.