"User Not Activated" error dialog when copying book over

When I copy a book from my MacBook Pro to my Nook reader, I get an error that says User Not Activated when I open the book.

I have upgraded ADE, deregistered and re-registered the device. Deregistered and reregistered my laptop. Still no luck. I can open the books just fine on the MacBook, but can't seem to get them onto my reader.

Please help!

Thanks.