$(document).ready(function () {
    Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(onRequestStart)
    Sys.WebForms.PageRequestManager.getInstance().add_endRequest(onRequestEnd)
});
var hideLoadBlock = false;
function onRequestStart() {
    if (!hideLoadBlock)
        showBlock('');
}

function onRequestEnd() {

    hideBlock();
    hideLoadBlock = false;
}