In iDVD ’08, your slideshows are no longer limited to 99 images. You can now have up to 9,801 images in a slideshow. When you are playing a slideshow on your DVD player, it will number the slides (which are chapters) from 1 to 99 and then start numbering over again at number 1 (on the one-hundredth slide). This is normal and not something you can control when you author your DVD. It is a specification that applies to all DVD players.
Bastards!