Index: wp-includes/class-wp.php
===================================================================
--- wp-includes/class-wp.php	(revision 17488)
+++ wp-includes/class-wp.php	(working copy)
@@ -496,7 +496,8 @@
 	 */
 	function main($query_args = '') {
 		$this->init();
-		$this->parse_request($query_args);
+		if ( !apply_filters( 'wp_parse_request', false, $this, $query_args ) )
+			 $this->parse_request( $query_args );
 		$this->send_headers();
 		$this->query_posts();
 		$this->handle_404();