No miniature in Organizer, but photo can be opened in Editor

In some maps no miniatures of some photos are shown. The can be seen in the maps on de harddisk without a problem. If I open in Organizer the photo for editing in the Editor, there is no problem to edit the photo. If I save the photo it still cannot be seen in the Organizer as a miniature. Even when I copy the photo if a different format, or copy in windows the photo an import it in Organizer it wil not appear as a miniature in Organizer. What is going wrong what did I wrong?