Error

I am also having this issue.  I have tried most of the same steps as Matthew by restarting me laptop, uninstalling ADE and reinstalling.  I "borrow" books from my library website and then download them as EPUB.  They go into my download and when I double-click them they ask which app I wish to use.  I choose ADE and the book loads into ADE.  My Nook is attached to the computer and turned on and the Nook icon shows up.  At this point I always have clicked on the "new" book in the ADE list and dragged it to the Nook icon.  Everything is fine to this point but it does not cooperate beyond this.  Either it ACTS like it is moving the book but just spins and spins, OR I cannot click on the book in the bookshelf in order to drag it to the Nook.  At this point NOTHING responds to a click in the ADE program.  I am STUCK.  Has anyone had this issue and found the solution?  (I was successful just 2 weeks ago in following the above described steps and getting a couple of books onto my Nook, which is less than 6 months old.)

I am having the same issue and went through all of the same steps, to no avail. I hope someone will be able to help.