Based on the information given, I suspect that you have purchased a book where the bookstore has disabled the ability to copy and paste as a security/DRM measure. Unfortunately, there isn't much that you can do if this is the case. You can go to the library view in ADE and then right click on the book and select "Get Info." If copying is allow or disallowed it will say it there.
It#s very interresting. I could copy from the same book, before i changed the computer. The same programm, the same book...and it was possible to copy sentences. Now, no chance.
And that happens to all my books