Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(beginReq);
Sys.WebForms.PageRequestManager.getInstance().add_endRequest(endReq);

function beginReq(sender, args) {
	// shows the Popup
    $find(mpeRoller).show();
}

function endReq(sender, args) {
	//  shows the Popup
    $find(mpeRoller).hide();
}