ADE 4.5 stopped showing library

ADE 4.5 appeared to get corrupted, stopped properly showing books or allowing downloads from the public library. I have a great many books in the ADE library. Following some advice here, I renamed the "My Digital Editions" folder, and new books are downloaded and show up in the newly created MDE folder. I still have all of the old books in the renamed folder, but I can see no way of getting them into the non-corrupted folder. Copying into the new folder doesn't work.