If you have AIM for Mac, which I do, you can go to the me section on the toolbar labeled with Buddies, Lifestream and ME. There should be text that says Buddy Lists That I'm on. Click on that, and it...
Get a different screen name, sign on, add the person to your buddy list, and see if they are online. If they are offline when you sign on with your old SN, but online when you sign on with your new...