Something wrong with the way you set up categories, I'd say, or you added the links to the header menu wrong (if done manually) or your dropmenu thing isn't working. The proper URL for a sub-sub category should be like cpath=107_108, where 108 is a subcategory of 107. Your Machines>Saws>Hand Saws is just cpath=108 where the Saws category id is 107.