There's been a problem with AIM for me for quite some time. The SN I've had for over 4 years suddenly won't display any of my buddies. It labels them as all logged off so I'm just dealing with it now >.>
What error are you getting when you try to get onto AIM? Like, can't connect etc?
get 6.9 or rollback to to previous versions such as 6.5. That one worked very well.
Alot of the time when that happens, just right click the AIM icon in the taskbar and "exit". Then restart it. AIM is a very buggy IM app.