MVC 4 $Ajax JSON Request returns status 0, statusText: "error" -

i trying update value on page every 5 seconds using jquery $.ajax, code used work fine, after deployment production server appears randomly failing. on pages work, , on others if fails error: status 0, statustext: "error".

can spot errors misnomers in code / markup?

i use call method every 5 seconds:

setinterval(function () {             updatemessages(); }, 5000); 

updatemessages looks this:

function updatemessages() {     $.ajax({        beforesend: function () { },        complete: function () { },        type: "get",        url: '@url.action("getunreadmessagesjson", "message", new { area = "" })',        contenttype: "application/json; charset=utf-8",        datatype: "json",        success: function (result) {            var newunreadmessages = result.unreadmsgcount;        },        error: function (rsult) {            console.log(rsult);        }    }); } 

my server code (action) inside mvc controller looks this:

public actionresult getunreadmessagesjson() {     int unreadmessages = 0;    try {        unreadmessages = messageservice.getunreadmessagecount(websecurity.currentuserid);    }    catch (exception) {        throw;    }    return json(new {        unreadmsgcount = unreadmessages        //,unreadmessages = unreadmessages    }, jsonrequestbehavior.allowget); } 

when use fiddler2 analyse request on local machine see in response:

http/1.1 200 ok cache-control: private content-type: application/json; charset=utf-8 server: microsoft-iis/7.5 x-aspnetmvc-version: 4.0 x-aspnet-version: 4.0.30319 x-powered-by: asp.net date: wed, 31 jul 2013 17:38:50 gmt content-length: 20

{"unreadmsgcount":3}

which looks , expect, never see request when site live. fiddler2 never shows outgoing ajax request, google chrome's console shows:

object {readystate: 0, getresponseheader: function, getallresponseheaders: function, setrequestheader: function, overridemimetype: function…}

which has status:0 , statustext: "error" inside. nothing more.

how on earth go investigating issue if there nothing wrong code? has seen before?

edit

after testing issue several browsers including ie, firefox , safari appears issue limited google chrome. have submitted bug report here , update post response get.

thanks,

explicitly set text/json follows

 return json(new {    unreadmsgcount = unreadmessages    //,unreadmessages = unreadmessages  },   "text/json", jsonrequestbehavior.allowget);