[Zope] Stupid newbie "Tree Tag" Question

Hi All, I'm trying to create navigation widgets in DTML documents, and am having *MAJOR* problems getting the tree tag to work. I've gone back to the simplest case to try to figure out what's going on, which is the construct: - <dtml-tree> <dtml-var getId> </dtml-tree> However, this returns *NO* results - if I fire it and look at the source of the rendered page, where I expect a tree I see: - <TABLE CELLSPACING="0"> </TABLE> I can see that the <dtml-var getId> works *outside* the tree, but isn't firing *inside* it. Initially, I thought that this might be a permissions issue, but this would seem to suggest not. All input gratefully accepted... TIA, Cheers, PhilK