It might be worth going to the library website online and seeing if the loan really has been returned or not.
ADE does not always delete returned books, just marks them invalid and you then need a separate delete.
Once the loan has been returned, future attempts to return it could well give E_BAD_LOAN_ID
How do I then do "a separate delete" after a book has been "marked invalid"?
I just take the same path as I would to return the book but instead of returning it I remove it from my library. When the tittle expires it is automatically returned.
I have deleted the books from my library in ADE even though I could not return them.. However the public library thinks they are still on loan. I cannot borrow another book because it thinks I still have 3 (maximum) on loan. I have only just begun to use ADE with my new ereader. I am disappointed to find bugs in the software so soon.
I seem to have solved the problem. I de-authorised the computer and the reauthorised it.