I think mine is yahoo, e-buddy, and have no trouble at all, though when talking to people on msn, they regularly have problems with freezing screens, logging them off and worse still, viruses.
I HATE msn everytime I have installed it my computer has slowed sown - and its not a vista issue - I have found the same with every computer system I have had regardless of which windows it has been-
do yo know you can add msn contacts to yahoo now?
anyway - just a thought on msn