title: jQuery.ajax() to json url is returning a string instead of a json object
body: <p>I'm having a problem where the data object passed to my complete() callback function is not a json object, but rather is an [Object object]. I can see a string of my json response in data.responseText.</p>
  
  <p>Here is my jQuery .ajax request:</p>
  
  <pre><code>$.ajax({
    url: 'api.php',
    dataType: 'json',
    data: {
      command: "GetBlacklist"
    },
    type: 'POST',
    error: function(jqXHR, textStatus, errorThrown)
    {
      messageDiv.append("Error: " + errorThrown + "&lt;br /&gt;");
    },
    complete: function(json)
    {
      $('.blacklist textarea').text(json.message);
      messageDiv.append("Blacklist loaded.");
    }
  }); 
  </code></pre>
  
  <p>And here is the response that is being sent:</p>
  
  <pre><code>{"message":"success","result":0}
  </code></pre>
  
  <p>It evaluates to valid JSON, and I am sending the correct json content-type headers from the server. Stumped on this one!</p>