I recently installed PHP 5.1.4 on Apache 2.2 using the modified php5_apache2.dll. After using apache and php for several weeks i realized that httpd.conf had the wrong path to the php.ini file (the path in http.conf was incorrect). when i modify http.conf to the correct path, php stops working. PHP works only when httpd.conf is configured to any path other than the correct one.
I also tried using the newer php 5.2 install with php5_apache2_2.dll with the same results.
This problem is very confusing to me.