We'll need to check the logs on the computer about this. While it can relate to a problem on the MSN files, there are also other possible factors. For example, Internet Explorer-related configuration couold be causing this. MSN uses Internet Explorer as its backbone in the browsing processes. Another possibility is an operating system-related failure.

How do we check on which might have caused the problem?

1. Restart the computer and reset Internet Explorer:

    a. Before you start MSN, click Start and type inetcpl.cpl in the Start Search area; then press enter
    b. In the Internet Properties/Options, go to the Advanced tab and proceed to reset through the button near that window's bottom part.
    c. Try signing in and check if the issue persists. Proceed to the next part if it does persist

2. Verify that Windows Updates are actually up to date.

    a. Click on Start and type Windows Update and it should show in the list
    b. Select it as it comes up and check if there are updates that you need to download and install
    c. If the issue persists after an update of Windows, proceed to part 3

3. Check what module caused MSN to end/crash.

    a. Click on Start
    b. Type eventvwr and press enter
    c. In the Event Viewer Window, open the Windows Logs at the left side.
    d. Select Applications
    e. Click Filter Current Log at the right side
    f. Put a check on ERROR
    g. Change <All event IDs> to 1000
    h. Click Ok
    i. In the list at the middle, look for at least 3 events/items that show msn.exe as Faulting Application Name
    j. Provide me the Faulting module name and the date.

We'll check on that and provide you the appropriate action to resolve the issue.

If the error comes up as you were signing in or while you are trying to load e-mail or do something on the e-mail section, follow the steps to rename SDF:
http://answers.msn.com/thread.aspx?threadid=942abfe7-577a-4fa0-8eef-a7d88a7e5677