Passing js object as json to jquery?

I have the following but it's not working, I read somewhere on the stackoverflow that it works like this but I can't seem to get it to work.. it errors... am I doing something wrong?

If I do pass data like this - it works -- so I know my service is working

//THIS WORKS
data: "{one : 'test',two: 'test2' }"


// BUT SETTING UP OBJECT doesn't work..

var saveData = {};
saveData.one = "test";
saveData.two = "tes2";


$.ajax({
    type: "POST",
    url: "MyService.aspx/GetDate",
    data: saveData,
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    success: function(msg) {
        alert(msg.d);
    },
    error: function(msg) {
    alert('error');
    }

});