Im gonna have to go with trillian. I use it for AIM and YAHOO and the only problem it was giving me was the browse plugin I tried to install. But all I had to do was upgrade, and now I have had no more problems.
and.... http://www.cs-lite.com
i know about 4 months ago you were able to get a cracked full version here but i havent been there since. So it might have changed.