Browser displays source of php files instead of supposed output on random basis

Hello. Randomly the php-source is displayed instead of the output (http://www.engstringen.ch/). 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