Are these DRM books or DRM-free ones?
If DRM-free, try using the free Calibre software; much better than ADE except for lack of DRM support.
If they are DRM books, does that bookeen support Adobe DRM ebooks?
If they are DRM and the bookeen is meant to support DRM, try the older ADE version, much more reliable (see below).
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
Some people have found ADE trying to upgrade automatically.
It appears (not 100% sure) that if you install ADE2.0 as a new install (not as an upgrade) that your 1.7.2 will continue to run.
Probably best to say no if 2.0.x installation asks if you want to migrate your library.