If your running xp or vista you could try a restore point before you started having this problem, other option would be to uninstall msn from 'Control Panel' 'Add or Remove programs' and then re-installing. If there is a updated version of your browser download and re-install new version. This may clear the problem.
One other thing before uninstalling, export your favourites to a file on disk so once you re-install you will be able to import them back. I dont know if uninstalling removes your favourites so better to be safe than sorry.