I have the same issue. I'm using Windows 8 Developer Preview Build 8102. I receive an error trying to log on to my AIM account, directly through AIM - "Connection error. Please try signing on again.", then it gives me the options to "Try Auto Configure or change your Settings manually." I still have no solution for this issue myself. I have a WiFi connection and I have not tried a direct connection - thus, my computer is too far from the Router to establish a wired connection.
Currently, I used Trillian to access my AIM account. That and Pidgin do work fine to establish a connect to AIM. I have tried re-configuring my AIM connections several times, even with the older connection settings - mentioned above. No luck simply with AIM.
If anyone figures a solution to this, other than a direct, wired connection, please inform.