Why am I getting corrupt, jagged photo in my iPhoto photo book?

I am trying to submit a extra large format book. When I make a pdf to check the book before sending there are problems. The dust cover comes out great, but the photos on the interior pages are all jagged and corrupt. I set them up as 300 dpi (which what is recommende I believe). I've updated my photo library files and deleted the excisting com.apple.iPhoto.plist preference file in the preference folder in the Library...which again was recommended on line. I am using the latest version of iPhoto '11. I don't know what to do next. I've spent a LOT of time on this wedding book and would like to have it published. I'd be really grateful if someone can give me some answers so I can order the book. I'd even settle for an Apple phone number where I could call to get answers. Thanks so much!

Dennis