p：blockui禁用Ajax

I have a problem, I'm using p:blockUi to block the full body of my page. The problem is that the AJAX events stopped to work, actually they only work once and then never again.

¿Does anybody now how I can fix it?

Here is my code:

<h:form id="formMenu">
    <ul class="menu">
        <li><p:commandLink action="alta" value="Alta" id="btn_alta"/></li>  
        <li><p:commandLink  value="Tramitaci&oacute;n" id="btn_tramitacion"/></li>  
        <li><p:commandLink  value="Bajas" id="btn_baja"/></li>  
        <li><p:commandLink  action="salir" value="Salir" id="btn_salir"/></li>          
    </ul>

    <p:blockUI block=":full_page" trigger="btn_alta,btn_salir,btn_tramitacion,btn_baja">
      <h:panelGrid columns="1">  
        <h:graphicImage value="/resources/img/ajaxloadingbar.gif" 
                        style="horizontal-align:middle; vertical-align: middle;"/>  
        <h:outputText value="Cargando..." style="white-space: nowrap;"/>  
        </h:panelGrid>
  </p:blockUI>
</h:form>