I'm using DE2. I had no problems with the previous version --- 1.7 I think. But have had nothing but problems since going to DE2.
My operating system is Windows Vista/Home.
I use a Nook simple reader. I have had one for a little over a year. My original Nook went bad at and it was replaced under warranty. Similar timing to updating to DE version 2.
The books work okay on the computer but will not open on the Nook. Message is not authorized. But, everything seems to check out okay.