I think you have a better chance to get a helpful reply if you ask in the Digital Editions forum.
Thank you Pat, I will do that.
The error message is documented in the KB: http://helpx.adobe.com/digital-editions/kb/e-lic-already-fulfilled.html
When you open a book in Adobe Digital Editions, you get an error stating that another user account has the book locked:
Check the Adobe ID used to currently authorize Adobe Digital Editions. If it is correct, contact the e-book provider to have the activation reset for the e-book. After the activation is reset, download the e-book again and it is associated with the account activated in Adobe Digital Editions.