I hope zope-dev is the right list to post this - I'm runining zope 2.2.2 on linux with python 1.5.2 Here's the set-up. I create a python class to act as a base class for a ZClass. I create a folder in Products called bugtest. Create a python class called bugtest. create and __init__.py file to register the base class. Restart Zope, see I have a new product called bugtest. Enter the bugtest product and create a ZClass the has bugtest as a base class. Everything works fine. Edit the python file bugtest.py - type in 'import x' (import something that isn't int the PYTHONPATH). Restart Zope. The bugtest product isn't shown as broken. Open the folder and everything in the folder has the 'product' icon. Try and create a new ZClass anywhere, and it fails. This is a sneaky bug because nowhere does zope tell you where or what the problem is, and it has the side-effect that you can't create a new ZClass. Could someone confirm this?