Rebinding events in jQuery after Ajax update (updatepanel)

Use the following code, You need to validate the control will use the datapicker:

<script type="text/javascript" language="javascript">

         Sys.WebForms.PageRequestManager.getInstance().add_endRequest(addDataPicker); 
         function addDataPicker(sender, args)
         {
            var fchFacturacion = document.getElementById('<%= txtFechaFacturacion.ClientID %>');
            if (fchFacturacion != null) {
               $(fchFacturacion).datepicker({ onSelect: function () { }, changeMonth: true, changeYear: true, showOn: 'button', buttonImage: '../Imagenes/calendar.gif', buttonImageOnly: true});}
         } 

    </script>

     <asp:UpdatePanel ID="upEjem" runat="server" UpdateMode="Conditional">
       <ContentTemplate>
              <div id="div1" runat="server" visible="false">
                  <input type="text" id="txtFechaFacturacion" 
                      name="txtFechaFacturacion" visible="true"
                      readonly="readonly" runat="server" />
              </div>
       </ContentTemplate>
     </asp:UpdatePanel>