Did you ask MSN support why you can't open your messages? (emails?) or folders? https://support.msn.com/default.aspx?locale=en-us
To use the support, choose and entry out of the list and you'll be directed to a form where you can describe your problem.
You could try upgrading to IE7. If you don't like it, it can be removed again via add-remove programs. It does take some getting used to, but has features which are more like Firefox.
Alternatively, you could try setting your computer back to an earlier restore point. This would remove any recent updates or installations which may have caused the problem. If it doesn't help, it's easy enough to undo the change.
If you've never done this before, Go to Start / All Programs / Accessories / System Tools / System Restore
check the box to Restore my computer to an earlier time and click on Next. You'll see a calendar with highlighted dates. Choose one of the dates just preceeding these problems and allow your system to return to that date. See if the problem goes away.
For Vista: http://www.bleepingcomputer.com/tutorials/...43.html#restore
If that doesn't help, simply go back into System Restore and choose the option to undo the change you just made.
Did any of the above help?