Problems with php-cgi / apache

Hello list, I've got a shared hosting environment with the following services: Apache 2.0.51 PHP 4.3.11 under Fedora Core 2. PHP is used as module with Apache, but I want to switch to php-cgi, maybe with fast-cgi, because it seems to be a good option for a better security. So I did the following: - I added the following lines to my httpd.conf: -- snip -- AddType application/x-httpd-cphp .cphp AddHandler application/x-httpd-cphp .cphp Action application/x-httpd-cphp /usr/bin/php -- snap -- The suffix .cphp was chosen just for testing purposes, so my other scripts still work with mod_php4. This is to be changed when it is running. - I've got a small, simple php-script like this: <?php phpinfo(); ?> with the suffix ".cphp". When I try to open this file, I receive an error 500 "Internal Server Error". The error_log says "Premature end of script headers: php". CGI is configured right, because Perl Scripts will run, has anybody an Idea what may be the error? Thank you in advance. Sascha