I'm having problem loading a json resource from a local rails app with jQuery 1.4.4

The json is valid (based on jsonlint.com) and I can download it properly if I'm requesting it from other sources.

In webkit (Safari), I got this error:

Failed to load resource: cancelled

Response Header on Firebug:

Content-Type application/json; charset=utf-8
Set-Cookie geoloc=toulouse; path=/;
Connection close
Server thin 1.2.7 codename No Hup

jQuery code to load json:

$.getJSON("http://127.0.0.1/search_agenda",
  {'edition': edition,
  'categories': categories},
  function(data){
    console.log(data);
  }
});