According to GeekNews either Trillian isn’t working or AIM is doing something to keep Trillian from working! Depending on who’s perspective you want to take, there is either a bug in Trillian or AOL is playing games again to keep non AIM users (and non-captive ad audience)from connecting to AIM servers. I sincerely hope AIM isn’t being stupid again!
Trillian has released version 0.721 in response to this problem and it should be working fine now. The 0.72 release, which was just released yesterday has a new auto update feature, so if you grab 0.721 you’ll get that too!