Apple Motion quits after message 'missing Magnetic Mask Files'

Apple motion (6.3) shows me the message 'this project contains layers with Magnetic Masks that require a re-analysis', when I click on OK Motion quits. What to do? I have already thrown away the magnetic mask folder from 'Users/[YourUsername]/Movies/Motion Projects' and opened Motion in reset-modus, and renamed the video's I used with the Magic Mask ... but it keeps quiting after the message. What to do?

Magic Mask