I used to have this problem last year when i used trillian, and i thought it was trillian causing it so i quit using it. Turns out its just their service? Its a shitty thing cuzz i think their messenger is so beautiful and the best (ONLY THE BEST WITH MSGPLUS installed of course
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But there should be some refresh thing or something for the contact list. Alot of people are having this problem though. They should have a real fix.