AJAX problem on Mozilla Firefox 31x and 32x, Sychronous XMLHttpRequest is deprecated.

AJAX problem on Mozilla Firefox 31x and 32x, Sychronous XMLHttpRequest is deprecated.

I have an adding form that allows to upload also a file, here's my code:

$("#frm_add").on("submit",function(e)
    {     
        var formObj = $(this);
        var formURL = formObj.attr("action");
        var formData = new FormData(this);
        var addnew = $.ajax({
            url: formURL,
            type: 'POST',
            data:  formData,
            mimeType:"multipart/form-data",
            contentType: false,
            cache: false,
            processData:false
        })
        addnew.done( function(data, textStatus, jqXHR)
        {
            if(data == "Saved")
            {
                $("#msgid").empty().removeClass().addClass("msgid-ok").append("Record Successfuly Save").fadeIn("slow").fadeOut(6000); if ( console && console.log ) {console.log(data);}
                $("#contentdata").load("phps/list.php");
                txtClear();
            }
            else if(data == "NS")
            {
                $("#msgid").empty().removeClass().addClass("msgid-ok").append("No Record Save").fadeIn("slow").fadeOut(6000); if ( console && console.log ) {console.log(data);}
            }
            else
            {
                $("#msgid").empty().removeClass().addClass("msgid-err").append("Saving Record Failed <br>" + data).fadeIn("slow").fadeOut(6000); if ( console && console.log ) {console.log(data);}
            }
        })
        addnew.fail( function(jqXHR, textStatus, errorThrown)
        {
            $("#msgid").empty().removeClass().addClass("msgid-err").append("Server Error #ADDGENERR").focus().fadeIn("slow").fadeOut(6000); if ( console && console.log ) {console.log(jqXHR + textStatus);}
        })
        e.preventDefault();
    });

But I got no response instead this is what on my console:

Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience. For more help http://xhr.spec.whatwg.org/

Can anyone help me to figure this out? I'm willing to give all my web page code including the PHP file.