Problem with JsonResult exception

I have controller action which returns JsonResult and is consumed by jquery ajax get request. All works well on my well my dev machine but when copied on production hosting I get below exception on last line controller action:

[AcceptVerbs(HttpVerbs.Get)]
public JsonResult Single(int UNIQUE_NO) {
  ...
  return Json(data, JsonRequestBehavior.AllowGet);  // < here exception is thrown
}

Method not found: 'System.Web.Mvc.JsonResult System.Web.Mvc.Controller.Json(System.Object, System.Web.Mvc.JsonRequestBehavior)'.

Exception is being captured by ELHAM.

Platform: ASP.NET MVC 2 Beta

Dlls included with app (Copy local : true): Microsoft.Web.Mvc, MvcContrib, MvcContrib.FluentHtml, MvcContrib.TestHelper, Rhino.Mocks, System.Web.Mvc, System.Web.Routing

What is going on here? What/Where should I be looking for this? (as mentioned above I dont get this exception on my dev machine where json result object is generated as expected and returned to caller)

Here is call stack (ELMAH):

System.MissingMethodException: Method not found: 'System.Web.Mvc.JsonResult System.Web.Mvc.Controller.Json(System.Object, System.Web.Mvc.JsonRequestBehavior)'. at NN_AccessToWeb_MVC2.Controllers.HomeController.Single(Int32 UNIQUE_NO) at lambda_method(ExecutionScope , ControllerBase , Object[] ) at System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters) at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext c开发者_StackOverflow社区ontrollerContext, IDictionary2 parameters) at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary2 parameters) at System.Web.Mvc.ControllerActionInvoker.<>c__DisplayClassa.b__7() at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func1 continuation) at System.Web.Mvc.ControllerActionInvoker.<>c__DisplayClassa.<>c__DisplayClassc.<InvokeActionMethodWithFilters>b__9() at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodWithFilters(ControllerContext controllerContext, IList1 filters, ActionDescriptor actionDescriptor, IDictionary`2 parameters) at System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName)

---

Try returning a new JsonResult:

return new JsonResult {
    JsonRequestBehavior = JsonRequestBehavior.AllowGet,
    Data = /* you model goes here */,
    ContentType = "application/json",
    ContentEncoding = Encoding.UTF8
};

---

return Json(data, "application/json", Encoding.UTF8, JsonRequestBehavior.AllowGet);