[jQuery] Ajax call problem with Firefox

[cindy]

There is a device with web server running. My code will check
periodically the status of the device.When I pull the network cable
from my laptop. I found that firefox can still response the request
sometimes. It seems firefox has cache some response. IE works fine.
Does some one have same experience?

My code is following:
asyncRequest:function(queryStr, cb, errorfn)
        {
         return $.ajax({
            type: "get",
            url: rap_util.urlroot,
            data: queryStr,
            error: errorfn,
            success: cb,
            async: true,
            dataType: 'xml'});
        },

function getDefaultPageHandle(rXml, textStatus)
{
        $(rXml).find("response").each(function()
        {
         var pageType=$("main_page_type",this).text();
         showPage(pageType);
    });

     if(defaultErr==true &&pageStatus=="ld")
    {
        $.unblockUI();
        defaultErr=false;
    }


        setTimeout("isFactoryDefault()",getDefaultPageTime);

};

function getDefaultPageErrHandle(XMLHttpRequest, textStatus,
errorThrown)
{
        if(pageStatus=="ld")
        {
                $.blockUI({ message: "<div  class='reboot_div'><div
class='ap_reboot_title'>Message</div><div class='ap_reboot_body_1'>AP
is down or web browser lost connection to AP...</div></div>" });
                defaultErr=true;
        }

        setTimeout("isFactoryDefault()",getDefaultPageTime);

};

function isFactoryDefault()
{
        rap_util.asyncRequest
("opcode=get_default_page_type",getDefaultPageHandle,getDefaultPageErrHandle);
};