javascript freeze when entering a link that starts with /

As a temporary solution, you could disable the menu_editor_path_autocomplete sub-module, which is not absolutely required for menu_editor to work.
(i will see why this is happening, hope i can tell more soon)

Ok, this is the solution:

<?php
function menu_editor_path_autocomplete($string) {
?>

has to become

<?php
function menu_editor_path_autocomplete($string = NULL) {
?>

I will commit this soon.

Should be fixed in 6.x-2.2