There are lots (can't emphasize it enough) of bugs in ADE 2.0, which Adobe does not seem to show any interest in fixing.
If you can't easily find your old version:
Version 1.7.2, it is a little difficult to find, available on Adobe site for Windows and for Mac.
http://helpx.adobe.com/digital-editions/kb/cant-install-digital-editio ns.html
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