title: Handle 500 errors in JSON (jQuery)
body: <p>This JSON request:</p>
  
  <pre><code>$.ajax({
      url:jSONurl+'?orderID='+thisOrderID+'&amp;variationID='+thisVariationID+'&amp;quantity='+thisQuantity+'&amp;callback=?',
      async: false,
      type: 'POST',
      dataType: 'json',
      success: function(data) {
          if (data.response == 'success'){
              //show the tick. allow the booking to go through
              $('#loadingSML'+thisVariationID).hide();
              $('#tick'+thisVariationID).show();
          }else{
              //show the cross. Do not allow the booking to be made
              $('#loadingSML'+thisVariationID).hide();
              $('#cross'+thisVariationID).hide();
              $('#unableToReserveError').slideDown();
              //disable the form
              $('#OrderForm_OrderForm input').attr('disabled','disabled');
          }
      },
      error: function(data){
          alert('error');
      }
  })
  </code></pre>
  
  <p>In certain circumstances will bring back a 500 error in the form of:</p>
  
  <pre><code>jQuery17205593111887289146_1338951277057({"message":"Availability exhausted","status":500});
  </code></pre>
  
  <p>This however is still useful to me and I need to be able to be able to handle this correctly.</p>
  
  <p>For some reason though, when this 500 error is returned, my error function is not called and I just get a "NetworkError: 500 Internal Server Error" error in firebug.</p>
  
  <p>How can I handle this?</p>