MSN Messenger & .Mac email account

[ardveche]

In the last few days MSN has developed a problem. I can log in, and see my contacts, and they can see me, but if I don't speak to them for a minute or so they become unable to send me any messages. I'm using my @mac.com email and have tried it on both a Mac running Adium and MSN and on a Windows XP machine running MSN Messenger and the same thing happens. I've fiddled with various settings, I've changed my password, and I have no idea what else to try.