At the top of the Trillian window, does it say "My Contacts"? I'm trying to determine if it's loading your contact list(s).
Do you know if it connects to the appropriate services that you have configured for it? Since you reinstalled it, it's possible that the plugins for the IM services have become disabled... you might want to go to prefs, and make sure that there were checkboxes beside the services that you use.