[SOLVED] Fancybox POST

[eluser]RobertB.[/eluser]
Hello guys,
Any idea why this is not posting anything?
In the firebug's post tab nothing shows.
This only happens with fancybox.

The idea is to get all checked checkboxes ids in the fb div

Code:

$('#fb-submit').live('click', function() {
  $.ajax({
     type: "POST",
     dataType: "json",
     cache: false,
     url: "",
     data: $('#fb input[type=checkbox]:checked').serialize(),
     success: function(data) {
       $.fancybox(data);
     }
  });
});

Thanks