Browser randomly displays php source instead of supposed output

Hello. Randomly the php-source is displayed instead of the output (http://www.engstringen.ch/). Generally, the output is correct !!! It happens sometimes after 10 minutes of browsing. Sometimes it comes up with the first clikc on the site. This was the case when having installed apache 1.3 und php 4.1. After ugrading to apache 2 and php 4.3.4 the bug still occurs. But the browser shows now a file download dialog box for downloading the php -script instead of having executed it !!! The header of the response contains the php - mime type configured application/x-httpd-php. The apache config contains AddType application/x-httpd-php .php .php4 .php3 .phtml AddType application/x-httpd-php-source .phps Include conf/confixx_vhost.conf The confixx_vhost.conf contains lots of virtual host configured on a named vhost basis. php is minimally configured with './configure' '--with-mysql' '--with-apxs' Linux version Linux 2.4.20. Thanks for any hint Stephan -------------------------------------------------------------------------- Gloor Informatik Zurlindenstr. 215 a 8003 Zürich Tel: 01 461 24 11 Fax: 01 461 22 39 info@gli.ch