I had the same problem and have spent the past 2 days trying to get a couple of epub books I purchased from Diesel books onto my Sony Reader (PRS T1). I had a call in with the book company, a ticket opened with Sony but was going around in circles. My computer was recongnised by ADE, my reader said it was authorized to read and purchase Adobe DMI content but ADE would not recognize my reader (I unsinsalled/reinstalled, tried many combinations of pluging the device in and then opening the program...) I was about to give up when I tried one last shot and downloaded Calibre (calibre-ebook.com/download) and within 10 minuites I had the 2 books I purchased on my Reader!!! Very easy to use and it works!!!