A somewhat different "CGI Error"

Hi, I am hosting my WordPress site on a Windows based shared hosting environment. I know this “CGI Error” problem is a very famous issue when comes to hosting WordPress on IIS. Before you turn away from this post, let me assure you that my case will be probably different than the previous ones.

Before I upgraded to 3.0.1 (from 2.3.1), I have sorted out the pretty permalink isse via the wp-404-handler.php workaround. As a reference, my wp-404-handler.php file looks like this,

<?php
  $qs = $_SERVER['QUERY_STRING'];
  $pos = strrpos($qs, '://');
  $pos = strpos($qs, '/', $pos + 4);
  $_SERVER['REQUEST_URI'] = substr($qs, $pos);
  $_SERVER['PATH_INFO'] = $_SERVER['REQUEST_URI'];
  include('index.php');
?>

After I upgraded to WP 3.0.1, the pretty permalink is still working fine, but whenever I include the ‘index.php’ in the permalink, it only works on my posts, but I will get a “CGI Error” on pages.

For instances, I can access my site very well using the pretty permalink for the following post and page,

Post:
https://www.procto.biz/business-and-industry/how-geeks-screw-up-startup-top-10-techie-traits-that-kill-your-business/

Page:
https://www.procto.biz/services/

But when I include the ‘index.php’ in the url, the page url will cause “CGI Error”.

Post (this will work ok):
https://www.procto.biz/index.php/business-and-industry/how-geeks-screw-up-startup-top-10-techie-traits-that-kill-your-business/

Page (this will cause “CGI error):
https://www.procto.biz/index.php/services/

I think this does not happen before I upgraded to 3.0.1.

You may ask why do I need to make this work. The reason is because I am using ContactForm7 plugin in some of my WP pages, and ContactForm7 plugin requires the submission url in the latter form (with the index.php as part of the form submission url) in order to work properly.

Any guidance will be much appreciated. Thanks in advance!