Searching Google it appeared that the user profile was corrupt, but I found a fix at a different site about a MSN shortcut messing things up. Gave it a try and it works. No need in go into the new user profile bit.
The following file was the problem:
C:\Users\<user name>\App Data\Roaming\Microsoft\Windows\Network Shortcuts\My Web Sites on MSN
Note: This file is not present in my new profile. Also, the icon has the shortcut marker on it, but explorer says it is a folder. There is no file extension.
I deleted the offending file from the bad profile and MP Navigator started working!
Hope this is of help to someone else.
