[Zope] How do I find which object causes a 'No Authorization header found' error ?

[vio]

Hi,
I have a product with many classes, and an access bug. How do I find out which object is causing the bug? The traceback:

Traceback (innermost last):
         File /v/Zope-2.4.1-src/lib/python/ZPublisher/Publish.py, line 223, in
publish_module
         File /v/Zope-2.4.1-src/lib/python/ZPublisher/Publish.py, line 187, in
publish
         File /v/Zope-2.4.1-src/lib/python/ZPublisher/Publish.py, line 162, in
publish
         File /v/Zope-2.4.1-src/lib/python/ZPublisher/BaseRequest.py, line 463,
in traverse
         File /v/Zope-2.4.1-src/lib/python/ZPublisher/HTTPResponse.py, line 581,in unauthorized
       Unauthorized: (see above)

This traceback is not very specific, it says 'Where' there was an error 'inside Zope', but not 'Who' caused it 'inside MY code'. I guess I can go into Zope source and start modifying it a little to make it spit the info I want, but that's not really an acceptable solution, is it (sounds ugly). So again, what I want is to know where the problem is inside MY code, not inside Zope. Any help or tips?
Vio