[Zope] ZClass selection property

[David Little]

Hi,

I am trying to make a ZClass for an research ethics committee. In the
zProject class I have  added a property sheet including a selection for
projectType value = projectTypes and added a lines property in the root
folder "projectTypes" with the values. 

A combox comes up in the zclass property sheet with the right values
from the root/lines propperty but when I add a property sheet interface 
I get a error mesage:
	Error Type: AttributeError
	Error Value: read
When I delete the projectType property, adding a property sheet
interface works.

I have tried putting the projectTypes lines property in various places
without a change.

Any suggestions as tto what I should try next?

david