[Zope] AttributeError on __error_log__ instead of the actual error in 2.6.0

[Felix Ulrich-Oltean]

I'm trying to develop/debug a python product in Zope 2.6.0, and I can
no longer see meaningful error messages or tracebacks.  When an error
occurs, I get a "Site Error" page with a traceback, but the traceback
is for the following error:

AttributeError: __error_log__

I'm guessing Zope can't find its fancy new error_log, but the result
is I can't see what's actually going wrong with my product.

If I look inside the error_log object on my Zope, the Exception Type
is "NotFound", but the exception value is a big bunch of html markup:

<TABLE BORDER="0" WIDTH="100%"> <TR VALIGN="TOP"> <TD WIDTH="10%"
ALIGN="CENTER"> &nbsp; </TD> <TD WIDTH="90%"> <H2>Site Error</H2>
<P>An error was encountered while publishing this resource. </P>
<P><STRONG>Resource not found</STRONG></P>  Sorry, the requested
resource does not exist.<p>Check the URL and try
again.</p><p><b>Resource:</b> Integration instance at 8f5cbf0</p> <HR
NOSHADE> <P>Troubleshooting Suggestions</P>  <UL> <LI>The URL may be
incorrect.</LI> <LI>The parameters passed to this resource may be
incorrect.</LI> <LI>A resource that this resource relies on may be
encountering an error.</LI>  </UL> <P>For more detailed information
about the error, please refer to the HTML source for this page. </P>
<P>If the error persists please contact the site maintainer. Thank you
for your patience. </P> </TD></TR> </TABLE>

What's going on here?  How can I get a real traceback?  I notice there
was a traceback-related query on this list last week
(http://lists.zope.org/pipermail/zope/2002-November/125944.html), but
no answer was given - is no one else having this problem?

TIA,

Felix.