Problem since Upgrading to 3.01 with wrong headers being sent

I have created the following page: look.php
and have the following code, but it returns a 404 header even though the page loads.
I did not seem to have this problem in wordpress 2.9.2

If I remove the require(‘./wp-blog-header.php’);, the page returns the normal page header.

<?php
require('./wp-blog-header.php');
echo "b";

?>