Shoutbox

Hi, I was wondering if you could help me. MSN lets me start conversations and then its fine, but it won't let others start them. People are talking to me and I don't even know about it. It's actually starting to annoy me now and I was wondering how this can be avoided. I've tried it on other PCs so its not a PC problem, it still happens to me on Windows Messenger too. Can anybody help me?