Index: includes/menu.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/menu.inc,v
retrieving revision 1.414
diff -u -p -r1.414 menu.inc
--- includes/menu.inc	8 Oct 2010 05:07:53 -0000	1.414
+++ includes/menu.inc	11 Oct 2010 19:36:22 -0000
@@ -1001,7 +1001,7 @@ function menu_tree_output($tree) {
     }
 
     // Allow menu-specific theme overrides.
-    $element['#theme'] = 'menu_link__' . $data['link']['menu_name'];
+    $element['#theme'] = 'menu_link__' . strtr($data['link']['menu_name'], '-', '_');
     $element['#attributes']['class'] = $class;
     $element['#title'] = $data['link']['title'];
     $element['#href'] = $data['link']['href'];