You should check if Firewall Adobe Digital Edition blockt.
I have recently been having all kinds of problems with ADE. I have had ADE 3.0 installed for quite some time with no problems until very recently. Long story short I ended up deauthorizing ADE, and then couldn't authorize my computer again. I tried everything, uninstalling, reinstalling, rebooting, nothing worked. Finallly went into my administration account and ADE showed as authorized, but when I tried to add a library book it told me it wasn't authorized, so I deauthorized in my admin account, and reauthorized and it worked. Tried to add the book, and it transferred, then plugged in my Kobo Glo & was able to add the book to it as well. When I change from my admin account to the one I normally use, the book I just added doesn't show, & ADE doesn't show as authorized. None of it makes sense, but try running from your admin account and it may work for you as well.