[Zope-CMF] traversal barf in Opera

[seb bacon]

I'm getting a KeyError occasionally when I look at my page in Opera,
but not in any other browsers:

Traceback (innermost last):

< snip >

  File /usr/local/Zope/lib/python/DocumentTemplate/DT_Let.py, line 146, in render
    (Object: rootpath=&quot;absolute_url()&quot;)
  File /usr/local/Zope/lib/python/DocumentTemplate/DT_Util.py, line 334, in eval
    (Object: absolute_url())
    (Info: absolute_url)
  File &lt;string&gt;, line 0, in ?
  File /usr/local/Zope/lib/python/OFS/Traversable.py, line 119, in absolute_url
    (Object: Traversable)
KeyError: SERVER_URL

A reload usually gets rid of the problem.  Any ideas what's going on
here?  This is unlikely to be CMF-related, so perhaps I should copy
the query to zope-dev?

seb