Shoutbox

This is driving me and my contacts crazy.  I'm in Australia, and have a guy in the 'states whose messages only reach me 1/3rd of the time, at best (I can send up to 10, over an hour, and he will get none).  Someone else in Finland: our messages only have about a 50% success rate of reaching each other.  Both people say it rarely happens with anyone else, but I never have had it happen with anyone else, either.  I've been with the same ISP for 6 years, and have only had the problem for the last year or so.  I've tried using a direct connection and not going through a router, and I'm not using wireless.  I don't even get "this message could not be delivered to all recipients" - it just never reaches them.  I have no idea what's going on - with the new WLM feature of being able to sign in from multiple locations, I found that one pc was getting some messages, and the other one was getting the rest (though I think that WLM just didn't know where to direct the data packets).  I have no idea why this happens, and haven't been able to find anything by googling.  Any idea why this happens, and what I should do to fix it?