Ok, I'm still getting this problem. Desktop Win XP Home runs MSN 7.0. Lappy Win XP Pro also runs MSN 7. Windoze messenger has been uninstalled.
So I log in on the lappy and a few minutes later a pop up appears I'm logged out as I'm signed in on another machine.
Even worse, I know that I exited MSN on the home PC, and there was no icon running saying it was still alive. So why is the thing resurrecting itself, and yet it's not active as there is no icon