I can't download my book to my iriver story book, I get a msg - CE copy not allowed - No permission to copy this book - what do I do. I can read it on my laptop, but can't move it into my ebook.

I have downloaded a book, which I can open and read on my laptop, but I can't move it into my iriver story book.  A msg comes up with "CE copy not allowed - No permission to copy this book" - what do I do.  This is the first time this has happened.