XML and Flash

Hello,
Maybe someone can help me out. I have tried making a slide show with thumbnails (flash and XML) by using the tutorials, but even though I follow the tutorial to the tee. I cant ever get the thumbnails to appear. Also, when I preview the swf file only alternate large images come up. For example the first, third and fifth images will appear but the 2nd and 4th will not.
Any clues or hints as to why this is happening would be greatly appreciated.
Thanks