Download your B&N books from the "My Nook" section of their website. Then when you try to open any of those books in ADE, on the first time it will ask you for a username and password. The password is your 'default' (according to B&N account settings) credit card number, and the username is the name as it appears on that credit card.
Alternatively you can just forget about ADE and download the Nook for Windows 8/Nook for Windows or Nook for Mac applications, and those will automatically download and manage your Nook content. (edit: just noticed the last line of your message, sorry)
I just tried replying to the email in my iPhone. but it got bounced back.
Yes, I see you crossed out the last two lines.
Everyone knows, and Barnes admits, that their app does not work under Apples newest OS "Mountain Lion". Which is already 6 months old, and Barnes is not fixing their app.
I wanted to be able to drag all my encrypted Nook books into the ADE library, but it won't let me. Sure, I used your method last night, and it works (user name same as on credit card/ password = ccard number). And, yes, ADE remembers it from then on, and I can open any Nook book, BUT... it's kind of clunky that way, since each epub is several directory layers down, I can only list one book at a time.
The more elegant solution would be to have them in the ADE library. That way all my epubs could be listed together.
I figured if Barnes was a listed vendor, that ADE would let me put them in it's library. As it is, I just get an error when I try dragging them into the ADE library.
ADE doesn't have direct support for downloading from B&N. However once you do have your books downloaded you can add them to the ADE library. (The Vendor ID is just there to authenticate you to Adobe so that you can open the book once it is down).
For instance if I were to do this, I would create a folder under Documents called books, and then create a folder called nook (and one called Baen, and one called Feedbooks, etc...).
After I have them downloaded, then in ADE I would select 'Add To Library' (Cmd-O) to select all of them and add them to my Library. (and then repeat for new books, as needed).