Whenever you purchase a book it is DRM protected to the email address you used to register with that company. The email addresses all need to be the same - for your Adobe ID and purchased books - to make it easy. Adobe digital edition can then open all your purchased epubs and PDFs. The Adobe Id is the one you then register your edge with. I'm not quite sure how they would have opened before, perhaps you were only opening non DRM protected books? Where do your books originate from? Did you buy them or are they freebies?