problem with accessing file

I downloaded an e-book, through DE, by authorizing my computer. My daughter played on the machine and somehow de-authorized the computer and removed some of my e-books. My problem is that I cannot access the computer auhorized e-books. As soon as I load the ePUB file it requires me to authorised for access. Even when authorizing the computer again, it states that is not the original authorized user. Is there something I can do or are these books lost to me?