Asp.net MVC 4: Jquery Ajax status 12031

Problem:

This morning I got message that deployed website is not working.
After checking it out. I got ajax error, when I was loading particular method ex: GetJsonData(). All other methods did work fine.

Small investigation lead me to ActionResult.

so it was

Solution:

public ActionResult GetJsonData()
{
  var result = ...
  return Json(result);
}

change it to


public JsonResult GetJsonData()
{
  var result = ...
  return Json(result);
}


and promlem was solved. Next time always return correct result. )