jQuery.ajax callbacks are not firing

jQuery.ajax callbacks are not firing

I have an ASP.Net JSONP web service that I just created in hopes of taking advantage of the JSONP workaround for the XSS security "fix." It took me a while to finally get the AJAX call and web service to work together to return a HTTP 200 status, but that victory was bitter-sweet. Now, everything appears to be working fine, but I am not getting any data or errors to help me move forward with this project. Can anyone help me? Here is an example of my JSONP code:
    jQuery.ajax( {
        type: 'GET',
        contentType: 'application/json; charset=utf-8',
        url: 'http://www.domain.com/JSON/JSONP-EndPoint.asmx/MethodName?callback=?',
        data: { 'name' : JSON.stringify(ProductId) },
        dataType: 'jsonp',
        async: true,
        success: function (data, textStatus){
            alert('successCallBack called');
            jQuery('#score').html(data);
            jQuery('#score').hide();
            score = data;
            alert(textStatus);
        },
        error: function (XMLHttpRequest, textStatus, errorThrown){
            alert('errorCallBack called');
            alert('textStatus = ' + textStatus + '/nerrorThrown = ' + errorThrown);
        } } );

The web service is supposed to return a single value of integer. However, I have no idea what it is or is not returning. I am not getting any error messages, my alerts are not firing, and the value is not assigned in the callbacks.

I have verified most of the process using HttpFox. However, due to a bug in the plugin, I do not know what the return content is or is not.

Can anyone offer any advice on how to troubleshoot this further? I will not post the web service publicly, but I can privately.

Note: For additional background information, I created the JSONP web service using this tutorial as a guide.