This is how it works here...
I download the library book to ADE, then I close ADE. I connect my Nook, make sure it is seen as being connected, and then I open ADE. It takes a bit for it to recognize the NC is connected, and then I can click on the books I want to load to the Nook, and drag them to the Nook listed in ADE, and drop them.
If I have the Nook connected before I download the book to ADE, or ADE open before I connect the Nook, it doesn't work.
I hope that helps!
Once your device is plugged into the computer, be sure to "wake it up" by sliding the "N" to the right on your NOOK Color screen. Your computer and Adobe Digital Editions should now recognize it. In ADE, you should see "media" on the bottom left side of the program. Simply drag the book cover onto "media."
Let me know if you need further assistance,
I have a Mac, for the past 2 weeks i cant get my nook color to load on my desktop. I've tried different Macs and tried everything else I have found in these posts and nothing is working. ANy ideas?