This one came up while migrating a user to a new machine. They had a range of IE favourites that were needed for the new machine and after exporting the favourites to a shared file location I was expecting the import to be as simple. However the error “Not a valid bookmark file” was displayed.
The solution was to open the favourites file in Notepad and save it to a new file with the ansi setting for file encoding. Retry the import and you should be able to access the new favourites after the import is successful