When PHP 4 is compiled as a zeus ISAPI module the following code while cause Zeus to display a '502 Bad Gateway' Error Message.

<? 
  session_start();
  session_register(blah);
  
  echo "Hello World\n";
?>

I have both the CGI and ISAPI version running on this machine, if in the Zeus administration server I switch to the CGI version everything will work fine, and if I switch back to the ISAPI version once I have a session created everything will work fine as well, but if I close my browser and reconnect I will see a '502 Bad Gateway' Error message again.  You will then have to run the CGI version again just long enough to run the session_start() which will create you a new session, after you have your new session you can switch back to the ISAPI version and everything will work fine until you lose your session...