Error msg CE copy not allowed. No permission to copy". Why?

I am on a MAC that has ADE 2.0 & 4.0 that I have used in the past to transfer a book.  I get the same error message with either version of ADE when I try to transfer an EPUB book to my Nook.

I am visiting family using their Mac.  At home I had a problem with 4.0 so it switched back to 3.0.

Help.