Unable to sync purchased Audiobook

[TOPSEY147]

I had to set my computer back to factory settings and copy all my music and audio books back on. When I sync with I-Pod one purchased audio book will not sync and says computer not authorised for this. All my software is up to date and I have deauthorised and re-authorised computer. The book is showing in my store purchases and audio book library but will not transfer to my I-Pod. Can anyone help? Incidentally for some strange reason it is not showing in my purchase history in my account on the I-Tunes store!

I have now managed to transfer this book by authorising my computer with my old ID and old password, although it means I now have 3 computers authorised when I am only using one!!