I had the same problem, I got a 0x81000301 error, but it was not only effecting MSN , my browser, mirc nothing worked. I looked into what I just did and remembered deleteing a directory called NewsDotNet or something of that sort. So when I rebooted my computer id get an error about newdotnet.dll being missing. So I came across these instructions for anyone who is having the same problem:

PROCEDURE 2 (Uninstall from Hard Drive):

1. Double-click on My Computer.
2. Double-click on the C: drive.
3. Double-click on the Program Files folder.
4. Locate and double-click on the NewDotNet folder. If there is no
folder, please proceed to PROCEDURE 3.
5. Locate and double-click on the uninstall executable; it will be
labeled uninstallX_XX.exe. (“X” represents the version number of the
uninstaller)
6. After removal of our software, you may be prompted to reboot.
Please reboot after removing our software.
7. If this does not fully remove our software, please proceed to
PROCEDURE 3.

PROCEDURE 3 (Locate Backup Copy of Uninstaller and Uninstall from Hard
Drive):

1. Double-click on My Computer.
2. Double-click on the C: drive.
3. Double-click on the Windows or Winnt folder.
4. Locate and double-click on the uninstall executable; it will be
labeled NDNuninstallX_XX.exe. (“X” represents the version number of the
uninstaller)
5. After removal of our software, you may be prompted to reboot.
Please reboot after removing our software.
6. If this does not fully remove our software, please proceed to

Hope this helps 😀