Are you using a Sony eReader?
There is a bug in ADE that stops it reading library books if a Sony eReader is plugged in, even if you don't try to use the Sony.
There are lots of bugs in ADE2.0 (and 2.0.1). Try replacing ADE2.0 with the older but more reliable v1.7.2.
(You can have them both installed at once if you like.)
Version 1.7.2, it is a little difficult to find, available on Adobe site for Windows and for Mac.
The forum software is sometimes corrupting the link above. There shouldn't be a blank in 'editio ns.html'. The following redirects to the same page: http://tinyurl.com/diged172
no, i'm using a pc with windows 7. as i said, in the past this has worked flawlessly.
i tried installing version 1.7.2, but the same error appeared.
The only other thing I can suggest is to check your firewall. Maybe it has decided it doesn't like ADE for some reason.