If your site occurs a 500 Internal Server Error the most common are php settings in your .htaccess file. They will typically look like this:
php_value "register_globals" "1"
To fix this simply create a file named php.ini in your public_html folder, and remove the lines from the .htaccess file and paste them in your php.ini file. Afterwards modify them to something similar as this:
register_globals = On
If this still does not fix your problem, check the permissions of your files and folders. On a PHPSuExec server you cannot have any files with 777 permissions.
For security reasons you should keep all folders at 755 and files at 644.
Some applications do require that a file to have greater permissions than 644, but make sure you change the permissions on that file only
