Using WordPress Functions on a Non-WordPress File

I am trying to get all the permalinks from my site using the following code:

include "wp-blog-header.php";

		global $post;
		global $wpdb;

		$myposts = get_posts('numberposts=-1');
		foreach($myposts as $post) {
			setup_postdata($post);
			$files[] = between(get_permalink(), get_bloginfo('url')."/", '.php').'.php';
		}

		$file = $files[ rand(0,count($files)-1) ];

When running this code, I get a Broken Link Page. If I comment this code out (ie the include) then the rest of the script works fine. The script is located in the main directory which is the same directory as wp-blog-header.php is located.