Trillian sucks. When it works it works fine. But when there is a bug it's a huge pain in the ass. I've been using
gAim - it's open source/free, it's light, it connects to AOL/ICQ/MSN/Yahoo and more under one interface, has history, spell checker, etc. Took me a few days to get used to it and have not have any problems yet. It's been a year. Give it a go.