[mod_python] More ugly "make_obcallback returned no obCallBack!" errors.

These don't seem to have anything to do with bad paths.  Here's the situation:

I have two name-based virtualhosts, each using mod_python.  They both use a
number of handlers.  Here are the relevant directives in the httpd.conf for
each vhost:

  PythonAutoReload Off
  PythonDebug on
  PythonTransHandler handlers.translate::transhandler
  PythonHeaderParserHandler handlers.headers::cookies
  PythonHeaderParserHandler handlers.headers::formdata handlers.headers::login
  PythonAuthenHandler handlers.auth::check
  PythonLogHandler handlers.log::log

I'm using Apache/1.3.22 (Unix) PHP/4.1.1 mod_python/2.7.6 Python/2.1
mod_ssl/2.8.5 OpenSSL/0.9.6.

So here's what happens:  Each Apache "server" (i.e., operating system
process, as differentiated by PIDs) only seems to be able to serve one of the
two virtualhosts -- the other virtualhost will present "Internal Server
Error" with the logs listing errors importing modules for make_obcallback,
and the infamous "make_obcallback returned no obCallBack!" error.