there are reported many errors in writing empty files on cards with newer firmware on the emotions, search here in ll for.
preview looks fine but thats all, you cant zoom in because there is just the preview jpeg embedded, no data. i stopped to use the cards and work with compressed files only in the internal drive. works fine, although i prefered the times when cards still were working. some backs seem to work, some not. it seem to be not depending on the card type.