Rails 3 AJAX remote form call backs

I'm upgrading from rails 2.3.8 to 3.0.0, so I need to replace the remote_form_for helper calls with form_for(@object, :remote=>true).

I've been following along with Simone Carletti but I cant seem to get the ajax callbacks from rails.js to fire.

My generated HTML is:

<form accept-charset="UTF-8" action="/vendor_shipments" class="new_vendor_shipment" data-remote="true" id="formname" method="post">

The javascript I'm testing with:

jQuery(function($){ 
   alert('document ready');
   $("#formname")
      .bind('ajax:loading', function() {alert("loading!");})
      .bind('ajax:success', function(data, status, xhr) {alert("success!");})
      .bind('ajax:failure', function(xhr, status, error) {alert("failure!");})
      .bind('ajax:complete', function() {alert("complete!");});
});

The 'document ready' alert fires, and the ajax request is successfully executed (data is posted to the server), but none of the 'ajax:____' callbacks fire.

What am I doing wrong?

(for what it's worth, the form itself is loaded via ajax)