Stopped opening ebooks

ADE opens, but as soon as i click on a book it closes down the app - i tried uninstalling the 4.5.10 and reinstalled 3.0 - reauthorized - still the same issue - i reinstalled 4.5.11 and it actually opens the Getting Started guide, but still closes down when I try opening a book - everything was working fine Wednesday - i've tried installing into a different folder - no luck - any help out there? Thanks