[Zope] CMF puzzlement

Hi all, Just trying Zope and CMF for first time and finding it very hard. My URL is http://pkirk.net.dhis.org/captain and I have the default CMF installed. I can register. But if the new user changes skins, they can no longer clich on the 'Home" link. If they change back, it works again. Anyone know if this is a bug or am I setting up something wrong? Patrick