[Zope-CMF] Allowing anonymous user to modify an object...

[Josef Albert Meile]

According to the followin FAQ:
http://cmf.zope.org/doc/FAQ/permissions/faq1/view

You can do it by giving the permission of adding contents to the 
annonymous user. On my case, I have a product called Membership 
(which in fact is not a portal content because I don't want other 
users to see it) and I just check the box "Add Memberships" on the 
Annonymous column.

As anonymous, it only allows me to create it, but as soon as I am 
going to modify its properties I got the login form. The result is a 
Product instance with all its properties without any value.

How can I do to solve this problem?