[Zope] Q: why does id evaluates to <string>?

I have created a zclass and created some instances. When I look at them in the management interface, though they have an id when listed in a folder, when I click on the link to manage the object, there is no id on the contents page. When I try to reference the object in a URL, Zope returns <space> instead of the id. If this is comprehensible to someone and they know what I'm doing wrong - either in defining the zclass or referring to instances, could you enlighten me? Thanks. Craig -- Craig Allen - Managing Partner - Mutual Alchemy Web Architecture - http://alchemy.nu