Tracked down obscure problem that has cropped up occasionally since the
beginning. If AOLserver his hit with a domain name that's not bound to
the IP it is listening on, it tries to serve /global/file-not-found but does
not call registered preauth filters first. It does call registered procs,
though. This results in rp_handler being called, but not rp_filter, and
rp_handler dies because it expects rp_filter to have set up ad_conn. My
solution is to simply redirect to the URL AOLserver substitutes, without
the bogus domain name, which causes the file not found page to be delivered
to the user. The calls I saw were GET
http://www.google.com to my server's
IP - probably a security exploit for IIS or Apache sometime in the deep past.