how long has this been happening for? just one night? or longer? at random times, msn has trouble running, and when you try and sign in, it shows various different types of messages...username and password is invalid being one of them. these messages usually just mean that msn is having problems, and either has too many people using it or it is having technical difficulties. it usually is fixed within anything from 2 to 12 hours. could anyone be hacking into your account perhaps? hope iv been of help