Trouble with JQuery Ajax / ASP.Net

Experts,

I'm having some trouble getting some ajax functionality to work in all browsers.  The code IS working correctly in IE8 and Firefox.  However, it is not working in Chrome, Safari, or Opera.

Below is my JavaScript (i.e. using jquery-1.4.3):
 

var ResponseTimer = "";

$(document).ajaxError(function (e, xhr, settings, exception) {
    alert('error in: ' + settings.url + ' \nerror: ' + exception + '\nxhr status: ' + xhr.status);
});

function StartResponseTimer()
{
    alert('CIP Settings have been sent. Awaiting response from control.');

    CheckForControlRepsonse();

    //Start javascript poll timer:
    //ResponseTimer = setInterval('CheckForControlRepsonse()', 2000);
}

function CheckForControlRepsonse()
{
    $.ajax
    ({
        type: 'GET',
        async: true,
        url: 'http://localhost:52971/AjaxResponder.aspx?CallingPage=CIP',
        dataType: 'html',
        timeout: 0,
        success: function (responseData) { ProcessAjaxResponse(responseData); }
    });
}

function ProcessAjaxResponse(responseData)
{
    if (responseData != 'no-response')
    {
        //If ACK or NCK received then stop timer:
        //clearInterval(ResponseTimer);

        //Display messages to user:
        var message = '';
        if (responseData == 'ACK') message = 'CIP Settings Received By Control.';
        if (responseData == 'NCK') message = 'An error occured when atempting to send CIP\r\n settings to control. Please try again.';
        alert(message);
    }
}

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And here is my server side code that is handling the ajax request:
 

namespace XXXXXXXXXX
{
    public partial class AjaxResponder : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            string CallingPage = Request.QueryString["CallingPage"].ToString();

            switch (CallingPage)
            {
                case "HOME": HomeResponder(); break;
                case "CIP": CIPResponder(); break;
            }
        }

        private void HomeResponder()
        {
            //....
        }

        private void CIPResponder()
        {
            string response = "";

            //ToDo: Get response message from listener server.

            //Temp:
            response = "ACK";

            if (response != "") Response.Write(response);
            else Response.Write("no-response");
        }
    }
}

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When I run the site in IE8 or Firefox I get a javascript popup saying: "CIP Settings Received By Control." Which is just what I expect to get.

When I run the site in Chrome or Safari, I get a popup showing:

    Error in: http://localhost:52971/AjaxResponder.aspx?CallingPage=CIP
    error: undefined
    xhr status: 0

Which would be the ajaxError() handler being executed.

When I run the site in Opera, I get nothing.....

Please advise as to what I'm not doing correctly.  Thanks.