If I got a structure like this

Category 1
|_ categoryItem

This could be an example,

Cars I owe
|_ Volvo
|_ Audi |_ BMW

Cars I have sold
|_ Renault
|_ Mercedes

Then I would have a documentype pointing to one of the categories for displaying all the cars in the category. but if this documentype is pointing at Cars I owe and I sold we say the Volvo I would put the Volvo down to the other category but the documentype is still showing the Volvo like it show a cached xml file or something ? So I doesn't think it read the data directly form the database ? maybe someone could think of something here. And as my title if I go in and point the documentype to the category again and save it works.