Diggit Drupalextras

My site has lost it's list of Books at ../admin/content/book/list. My content list still displays all the book pages, but the child pages have lost their parents in the outlines. When I try to edit the book pages to re-establish the outline, or reassign a book page to a new parent, I get a user warning:
"user warning: Duplicate entry '264' for key 2 query: INSERT INTO book (nid, mlid, bid) VALUES (264, 3763, 325) in /home/content/b/c/h/bchccnet/html/drupal/modules/book/book.module on line 466."
I have checked the node and book tables, and the data is still there. Anyone have any idea how I can bring back the books and their structures? Previous to this problem I did remove some unused modules and ran an update.php.
Any help is greatly appreciated.