Do you mean MSN Messenger? I think all messenger transfers suck including AIM, sometimes they are 1kbps, sometimes they run at 50kbps, even when both people have high speed broadband. I have MSN, and the websites transfers go up to 300kbps steadily, but my messenger transfer usually caps around 10kbps. May there be a problem with your software maybe?
Well it depends if you are on a p2p and you have people uploading off you then your transfer speeds will be slow but if you dont have p2p then I dont know what the deal is.