iChat buddies appear for 2 seconds, then disappear
I'm having the same problem, and none of the suggested solutions on various sites have helped. I removed the iChat .plists (all 5 of them, yes with iChat closed). I checked for misspellings in the Address Book. I even downloaded the (now antiquated) iChat client from aim.com to check the buddy lists in it, which were fine. But nothing I've done has gotten certain buddies to show up in the Buddies list of iChat (others do show up--it seems random which do & don't appear). AIM works fine, Adium works fine. But I want to use iChat so I can make use of the screen sharing feature (since "Back To My Mac" also does not work.) I fear we may have to chalk up iChat as another part of Leopard that is still only partially baked. 🙁