title: jQuery[number] was not called
body: <p>Ok, I have searched this question and have found numerous answers on it but none have worked for me. 
  I'm getting jQuery21006460414978209883_1395689439888 was not called error. 
  The AJAX call is done right, status is 200 and the php url that i'm trying to call, i have validated its JSON and it is a valid json according to jsonlint. 
  I'm using jsonp since it is a crossdomain call. 
  Any advise would help me debug this. 
  Here is my javascript code: </p>
  
  <pre><code>$.ajax({
      crossDomain: true,
      cache: false,
      type: "GET",
      url: "http://example.com/backend.php",
      data: "fdaf",
      //async: false,
      dataType: "jsonp",
      contentType: 'application/json; charset=utf-8',
      success: function(msg){
        alert("success"+ JSON.stringify(msg));
      },
      error:function (xhr, ajaxOptions, thrownError){
                  alert('error function status is : '+xhr.status);
                  alert('error thrown is:  '+thrownError);
      },
      jsonp: "callback",
      complete: function (requestState) {
          alert("working");
      } 
  });
  </code></pre>
  
  <p>My backend.php code is here: </p>
  
  <pre><code>&lt;?php 
  header('Content-Type: application/json');
  
  $arr = array('a' =&gt; "1", 'b' =&gt; "2", 'c' =&gt; "3", 'd' =&gt; "4");
  $tr =  json_encode($arr);
  
  echo $_GET['callback'].'['.$tr.']';
  ?&gt;
  </code></pre>
  
  <p>Please advise what I am doing wrong here. Many thanks! </p>