Missing bookshelves

I have been using Digital editions 4.5 without a problem until now.

When I open it all the Bookshelves have disappeared, along with the books that were on them.

When I add a new bookshelf it knows that the previous bookshelves are there somewhere and adds a new one with ahigher bookshelf number.  But that disapears when I shut down and reopen it. 

Any idea for a solution