can't open borrowed ebooks on my laptop anymore - no problems with my cybook!!!

Hello,
  I've an ebook since about 2 1/2 years (Cybook Odyssey) and, until a few weeks ago no problems.
But now I can't open any more from library borrowed books on my laptop; download works and whether I click the button to save the book on my laptop or to open it, Adobe says always:

                                               Error!Check Activation

When I click it the authorization information, I get the message that the computer has already been authorized.
I have uninstalled the previous version and installed the latest now.
With the previous version came an information that the document would be reviewed and a second information that even a previous download would not be complete and whether I would like to finish this.
alI the same, whether I click  "cancel" or "ok" - it's doing nothing - I only can close the program ....

Books, which I bought online, I can now - with the latest - version open again.

When I download the books from Library directly to my e-book, I have no problems by the way.
But the "handling" with the Laptop is much easier for me than with my Wi-Fi e-book ...
Maybe someone has an idea? I'm using Windows 7

By the way - sorry for my mistakes. I'm German - and not perfect in english writing.

If you like - answer in german....

GCaby