Table content disappearing when PDF'ing in FrameMaker 10

Recently when I've pdf'd a book in FrameMaker 10, some of the content in the tables is missing. It can be either text or graphics and usually occurrs towards the start of the book, but it won't be throughout the book. This doesn't happen with every book, only the odd one, but is very frustrating.

If I pdf the individual Frame file, it works perfectly, some of these files have been used in previous books and the books pdf'd OK with no problems. The computer is running Windows 7 with 12 GB of RAM.

Any ideas?