After a recent automatic update of Trillian, I was unable to connect to AIM. The console stated:

Error Code: 10054

After searching around and trying a bunch of things, I was unable to re-connect until I found the following in the Trillian Technical Support Forum:

1. Click Trillian > Connections > Manage My Connections.
2. Select your AIM account, click Change button.
3. Under the Connection tab in the Server section, click Reset, then Save Settings.
4. Click Trillian > Trillian Preferences > Plugins.
5. Disable AIM & ICQ by unchecking it.
6. Re-enable AIM & ICQ by checking it.
7. Click Close.
8. Click Trillian > Connections > Global Reconnect.

This worked for me and I was able to connect to AIM once again.