title: jQuery AJAX request does not return (no HTTP status code) and stays pending
body: <p>I have several requests like this:       </p>
  
  <pre><code>   $('#some-button').on('click', function(e) {
        e.preventDefault(); 
        $this = $(this);
        $.ajax({
           url: 'some_request.php/?q='+$some_id,
           dataType: 'json',
           success: function(data) {
              alert('success!')
           }          
        }); 
     });
  </code></pre>
  
  <p>I.e. lots of AJAX requests that get initiated on button clicks.  This request stays 'pending' according to Chrome - no JS alert.  No HTTP response code comes back.  I think it's just sat there waiting on a response and not getting it.</p>
  
  <p>Question is similar to: <a href="https://stackoverflow.com/questions/8724739/jquery-ajax-request-remains-pending">jquery $.ajax request remains pending</a> but the answer doesn't help.  Nowhere in my PHP or HTML code am I using the session.</p>
  
  <p>Any ideas?  Many thanks.</p>