Shoutbox

Hi, I'm using MSN Mac Messenger on Mac OS X 10.4, and I've been having problems with MSN/Adium the past few days - my contacts can't send me messages (they get 'The following message could not be delivered to all recepients' when they do so), and it only works when I send them a message first and even so, only for awhile. Can anyone help? I tried unblocking the firewall ports already but it doesn't work.