[Zope] pythonpath incomplete?

Hi, I have python 2.3.4 running on my server and I installed Zope 2.7.3. installation goes wel, but when starting zope, I get: File "/opt/Zope-2.7.3-0/lib/python/OFS/History.py", line 17, in ? import Globals, ExtensionClass, difflib ImportError: No module named difflib but difflib is installed in /usr/local/lib/python2.3/difflib.py so it seems zope can't see the normal python-libraries. How to solve this? I installed Zope 2.7.3 because my normal zope (2.7.2) stopped functioning (cause unknown) with exactly the same kind of import-errors. It ran without any problems before. thx, w.