Another question not answered. Outstanding since Oct 2014. I am having the same problem; as are many others. Who has the answer?
I had the same problem with Adobe Digital 4.0 so went back to 3.0 and it worked again.
I went back to 3.0, and still get the same error message when trying to transfer to my Nook Color. Since this has been an ongoing problem since 2014, I'm assuming you are on your own to find the answer, as Adobe will not help.