Vote

http://feedback.photoshop.com/photoshop_family/topics/publishing_book_ neither_pdf_nor_blurb_in_lr_4_1_not_possible_buttons_seem_to_be_withou t_any_function

The next-to-last reply of the feedback thread Dorin linked to, above, tells of one possible thing that someone fixed and got things to work afterwards:

“I just found the solution to my problem: I had used 1 Picture that was not part of the Books-Compilation as a Background Picture - after deleting it from the Book and using a Background-Picture from the Collection the Export to Blurb went fine.”

There may be but I am not experienced in the book module or collections in general, only reading posts about such, and am not at the right computer to experiment at this point in the day.

It seems like a way to tell if the book has an errant page or image that is preventing the Export would be to create two temporary copies of the book (or of the entire catalog if that makes more sense).  In one copy remove the first half of the pages, and in the second copy remove the second half of the pages.  If an Export works for one of these temporary copies with half the pages deleted, then the issue must be within those pages that were deleted.  If this initial delete-half experiment works, then make another temporary copy and try deleting a few pages at a time (5 or 10) from the half with the problem until the Export works, then you’ll know the problem is within those few pages, and you can do one more page-by-page deletion in a new temporary copy to see which page has the problem.

It would probably be wise to make a backup of your entire catalog before starting any such diagnostic procedure and do the experiments on that copy.

Great.  That’s easier than searching for a broken image.  Did disabling Graphic unlink something that wasn’t relinked when you re-enabled Graphic?  In other words, did the book change in some subtle way?

If things indeed are ok, you might add the description of your original situation and the magic incantation that apparently fixed it to the Feedback discussion Dorin linked, because the Feedback area is what Adobe pays attention to more, so if there’s a bug maybe Adobe can figure it out.