You are probably having this issue due to an outdated MSN profile. It can also occur when a corruption has occurred to your account settings in the MSN software. To resolve this, you may just need to update your MSN account information. Here's how:
1. Open Internet Explorer then go to
www.support.msn.com then sign in to your MSN account
2. Once signed in, click 'çhange MSN Profile' at the left of the page. Your account information will then be displayed. Please make sure everything is correct.
3. Click 'Save' below the page even when you did not change any information in your account.
After updating your MSN profile, try to sign in to MSN again.
If you are still unable to sign in, then you need to remove and re-add your account in the MSN software.This resolves most sign-in issues. However, the process of removing an account from the MSN software may delete the messages saved on folders on your computer so creating a back-up is necessary. For a detailed procedure of backing-up messages, removing and re-adding your account, I suggest that you contact the MSN Technical Support at
www.support.msn.com. They can give steps appropriate for your MSN version. =)