ADE has frozen since I added a pdf file.

Everything was fine, ADE and Nook all behaving - until I downloaded a pdf file using AE rather than Twinu (which I'd never heard of).

It was when I tried to move the pdf file onto the Nook that the problems started, The file did not transfer and the ADE opened with the pdf in view but refused to return to Library, No go back button visible and all options greyed out. What terrible thing have I done??

I did try and shift it by downloading another Epub book, but now that has frozen, can't turn pages or anything.

Any simple advice welcome as I'm a severe technophobe! Thanks.