1) If you have a custom away message or any of your Yahoo Friends have a custom away message, Trillian will crash when it trys to set your's or recieves one from a friend. (Found in the support boards of http://www.trillian.cc )
Don't auto away or use one of the default away messages to avoid this crash as often. You cannot protect yourself from someone else's custom away message from crashing you though.
2) Yahoo has once again changed the default servers for Yahoo Messanger. The new ones are:
The old server "scs.yahoo.com" continues to work, but you can only "see" folks who are logged into that one server.