jQuery BlockUI Plugin - Uncaught TypeError: Cannot read property 'parentNode' of undefined

Try this to solve.

$(document).ready(function () {

    $.blockUI.defaults.message = $('#your_ref_element');
    $.blockUI.defaults.baseZ = 1200;

    $(document).ajaxStart(function(){
        $.blockUI();
    });

    $(document).ajaxStop($.unblockUI);
});//end ready