Hi, my iPad is all set up as of last week; however, I added two new pdf books into iTunes by dragging them from my pdf file on my computer. This worked just fine last week and they synced to my iPad. Today, when I dragged two more into iTunes and tryed to sync it didn't work... When I click on "books", it is greyed out but I see the two new books there without check-marks next to them. If I click "sync books" I get a message that says: "Are you sure you want to sync books? All existing songs, moves and tv shows from the iPad will be removed". Can somebody help me? Thanks!"