[Zope-CMF] DiscussionItem view error

[Mark Gibson]

I'm allowing discussions for a piece of custom content.  I can create 
comments fine, but I'm having problems viewing them.

If I use:
http://mysite.com:8080/portal/qualifications/talkback/1039557500/discussionitem_view
without a problem, but If I use:

http://mysite.com:8080/portal/qualifications/talkback/1039557500
(not supplying the view explicitly)

I receive this error:
----
Error Type: TypeError
Error Value: __call__() takes exactly 1 argument (4 given)
Traceback (innermost last):

  Module ZPublisher.Publish, line 98, in publish
  Module ZPublisher.mapply, line 88, in mapply
  Module ZPublisher.Publish, line 39, in call_object
----
Not much to go on.  Any idea of what the problem might be?
Zope 2.6
CMF-1.3

Mark