A very small number of users have reported a nasty bug where their AIM serverside list was partially deleted. We have found the source of the bug and fixed it for Adium X 0.62 (available within 24 hours of this post).
For users who were affected, I’ve written a small program which will use Adium X’s preference files (which are independent of the serverside list though not sufficient to fully reconstruct it) to create an AIM .blt file suitable for importing via the official AIM client (File->Import while signed on). The .blt file (AIMContacts.blt, created on your desktop) contains all buddies which have ever been on an AIM account’s buddy list in Adium X; groups are not included, as Adium does not store that information locally, so they are all listed in the “Buddies” group. Hopefully this will help anyone who was unfortunate enough to run into this problem. We’re sorry for any inconvenience it caused 🙂