[Zope] Plone installation

When installing Plone I see a DCWorkflow in the tarball, but I already have one. Does the new on replae the old one or should it be installed over the old one? Also when trying to add my first Plone site, I get:- Zope Error Zope has encountered an error while publishing this resource. Error Type: AttributeError Error Value: get Does this sound like a common problem? What have I missed? Any idea where I should look to see what is wrong? -- John