[Zope] Can't create a MailHost

Hello Zopers, I tried to create a Mail Form as the How-To describes it, but it its impossible for me to get the first step done, creating the MailHost object. When I push the ADD button on the form to create the MaiilHost, it gives me back this error: Error Type : KeyError Error Value: manage_addMailHost I am running RedHat 6.0 with Python 1.5.2 and Zope 2.0b3. In the form to configure the MailHost I put the local host as the SMTP host, in which I have sendmail running at port 25. Thanks in advance, - Arkaitz.