This may indicate that MSN Explorer is having trouble using your current Internet Explorer settings.
Let’s reset your Internet Explorer Settings
1. Open Internet Explorer
by double-clicking on the Internet Explorer icon or selecting it from the Start menu. At the top of the window select Tools, then Internet Options. Note: if the Tools menu is not visible, press the Alt key.
2. Click here for instructions to clear Internet temporary files and cookies.
3. Choose the Security tab and click the Internet icon (it looks like a globe). Then click the Default level button if you can (sometimes this button is unavailable; this is normal).
4. Choose the Local Intranet icon, then click the Default level button if you can (sometimes this button is also unavailable; again, this is normal).
5. Choose the Advanced tab and then click the Restore Defaults button (in Internet Explorer 7 and 8, this is named the Restore Advanced Settings button). Click OK when you are done and try signing into MSN Explorer again.