note 25482 rejected from function.include by nicos

Hi you all! I'm short befor a nervous breakdown. Using PHP and installing it (on WAMP-inviroments) for years, i now have to use it on Red Hat Linux 7.3 (with actual Apache 1.x). My Problem: I cannot include some files in my PHP-scripts. The include path is defenitly correct in my php.ini. When i build some new file for testing (e.g. just "<? include("xyz.php"); ?> it works really great, but in a downloaded script (just same syntax) it gives me some error ("Failed opening for inclusion..."). Can anyone imagine what this is?? Thanks for any help! Regards, Toby