Can’t change permalink url after hitting ‘ok’ and ‘update’

Have you somehow hidden/removed the slug metabox? (is something like this located in your functions.php?)

function remove_post_meta_box() {
    remove_meta_box('slugdiv', 'post', 'normal');
}
add_action('admin_menu', 'remove_post_meta_box');

If that’s the case, it’s causing the error.
There is a Trac ticket for this already, but the only way to currently solve it is to remove it.