Forum 500 Internal Server Error instead of 404 Page Not Found

[محروم.كوم]

This Model-View-Controller Rewrite Rule causes any 404 errors to instead give a 500 internal server error:
Code:
RewriteRule ^(?.*?)(?:/|$))(.*|$)$ $1.php?r=$2 [QSA]
This is a part of the supplied .htaccess file from the vb4.0.4 package.

How do I make a proper 404 page not found error display without disabling that rule? __DEFINE_LIKE_SHARE__