Index: wp-includes/post-template.php
===================================================================
--- wp-includes/post-template.php	(revision 9995)
+++ wp-includes/post-template.php	(working copy)
@@ -686,7 +686,7 @@
 	if ( $menu )
 		$menu = '<ul>' . $menu . '</ul>';
 
-	$menu = '<div id="' . $args['menu_class'] . '">' . $menu . "</div>\n";
+	$menu = '<div class="' . $args['menu_class'] . '">' . $menu . "</div>\n";
 	$menu = apply_filters( 'wp_page_menu', $menu, $args ); 
 	if ( $args['echo'] )
 		echo $menu;