jQuery ajax:error runs even if the response is OK 200

I have a form which submit a form via AJAX with :remote => true. Looking at the server log and FireBug, I get the response 200 OK and it returns JSON in the form of:

{ "email": "test@test.com"}

then I have these two handlers:

$('#new_invitation').bind("ajax:success", function(event, data, status, xhr) {
    alert('test');
});

$('#new_invitation').bind("ajax:error", function() {
    alert('error');
});

and even if I get back a 200OK, it is the error handler that fires. The only time I managed to make the success handler work was when I send a empty response with 200 in the header.

I can't figure out why this isnt working :-S

EDIT 1------------ After doing these changes:

$('#new_invitation').bind("ajaxSuccess", function(event, data, status, xhr) {
    alert('test');
});

$('#new_invitation').bind("ajaxError", function(jqXHR, textStatus, errorThrown) {
alert('error');
    console.log(jqXHR.responseText);
    console.log(textStatus.responseText);
    console.log(errorThrown.responseText);
});

I am still getting the same error. The log stuff gives me:

undefined
my_email@test.com
undefined

Here is the code for the form (standard Rails stuff):

<%= form_for @shoot.invitations.new, :url=>shoot_invitations_path(@shoot), :remote => true, :html => {:class => 'form-inline'} do |f| %>
    <%= f.text_field :email, :'placeholder' => 'ex: test@test.com' %>
    <%= f.text_field :role, :'placeholder' => 'ex: Photographer' %>
    <%= f.submit "Invite", :class => 'btn btn-success' %>
<% end %>

EDIT 2 ---------

I did a few changes and now it seems my error is a parse error. I dont understand because this is the JSON I am getting back from the server (data.responseText), which seems all good:

{"email":"zxxczxc@test.com"}