Also looks like you are on Apache 1.3x, which may mean you need to edit your .htaccess to use the correct Handler (the application/x-httpd-php uses mod_php, which is being phased out)
Try copying /dh/cgi-system/php5.cgi to your /cgi-bin/ and adding the correct handler.
In the future, use a custom php.ini with these error directives and then you can better diagnose what the problem is by viewing the error_log you configure.
error_reporting = E_ALL
display_errors = Off
display_startup_errors = Off
log_errors = On
error_log = "/home/username/php_error.log"
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