Permalinks, IIS 6, PHP 5.2.1 (upgrade from 5.2.0)

[I hope “How-To and Trobleshooting is the correct forum for this…]

Hello,

Last week we, the hosting company I work for, upgraded from PHP version 5.2.0 to 5.2.1. And suddenly customers started complaining about permalinks stopped working and returning 404 errors. I am now trying to find the cause (probably changes in some of PHPs regular expression-like functions), but my guess is the WordPress developers here know more about the rewriting code of WordPress than I do to pinpoint it ??

For my test purposes I have created two identical application folders with one difference: One of them uses PHP 5.2.0 and the other 5.2.1. They both use the same php.ini file. The phpinfo() information is located here:
https://www.vevida.to/php/php520/phpinfo.php
https://www.vevida.to/php/php521/phpinfo.php

and both WordPress installations can are located here:
https://www.vevida.to/php/php520/index.php
https://www.vevida.to/php/php521/index.php

As you can see, a permalink like
https://www.vevida.to/php/php520/index.php/2007/02/21/lorem-ipsum/
works, and
https://www.vevida.to/php/php521/index.php/2007/02/21/lorem-ipsum/
does not.

We noticed the same behaviour with blogs/cms’s like ExpressionEngine, which we could “fix” with ISAPI_Rewrite. But I have not tested that thoroughly…
Is this a problem I (or better, the WordPress developers ;)) can fix by changing some code or functions? Or is this a problem with (some of) the PHP core fuctions which needs to be fixed by the PHP developers?

If anyone is capable of rewriting the .htaccess rewrite rules to ISAPI_Rewrite (https://www.isapirewrite.com), I would be more than happy to test them ?? ISAPI_Rewrite support within WordPress (next to .htaccess) would be a nice addition, for websites hosted on Windows/IIS.

Thank you in advance for any insights, pointers and/or help.

Best regards,
Jan Reilink, VEVIDA Services bv