[Zope] [Q] The Book's examples are working sporadically for me

I think I've got some kind of permission problem, since the examples in the "Book" concerning <dtml-tree> and <dtml-in expr="objectValues('Folder')"> etc., work on some folders and not on others. Can someone clear this up for me so that I can get consistant behavior? Thanks. Carl David david@uconnvm.uconn.edu