asp.net MVC / jQuery Ajax returning 500 Exception not JSON Result -

i have asp.net mvc 2 web application in middle tier controller actions catch exceptions, log, , rethrows exception. rethrow picked jquery ajax error handler

throw new exception(e.message); 

i making ajax call via jquery this

jquery.ajax({ url: '/controller/action',   success: function(data) {  },   error: function(jqxhr, textstatus, errorthrown) {          var error_json = json.parse(jqxhr.responsetext);  // returning error     var html_error = error_json["message"];   }  }); 

and reason jqxhr.responsetext not returning anymore , getting error when parsing responsetext. think may iis setting since switched new webserver. ** looking firebug there no more json response normal. see server response 500 exception **

looks iis 7 setting. in error pages --> edit feature settings --> select detailed errors. –