Strange behaviour....

Please help, it is very important....

I am trying to open modal panel, it works fine when there is NO validation error.

Scenario:
For example if there are duplicate number in text field, I am validating and render the form.

a) At this point, when I click "Update" button, modal pops-up for a second, and error message is displayed on the parent screen.

b) When I click again keeping duplicate number,  MODAL does not work and COMPLETE XHTML SCREEN is DISPLAYED TWICE.. :(

c) If I click again after changing to unique number in text fields, MODAL does not pops-up but message is displayed "Your request is in progress, please wait..." on the top-left corner of the browser....

Please suggest what I am doing wrong...

XHTML code:
----------
<!DOCTYPE composition PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
                             "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<ui:composition xmlns="http://www.w3.org/1999/xhtml"
                xmlns:s="http://jboss.com/products/seam/taglib"
                xmlns:ui="http://java.sun.com/jsf/facelets"
                xmlns:f="http://java.sun.com/jsf/core"
                xmlns:h="http://java.sun.com/jsf/html"
                xmlns:a="http://richfaces.org/a4j"
                xmlns:rich="http://richfaces.org/rich"
                template="layout/template.xhtml">
                      
<ui:define name="body">
   
    <h:messages globalOnly="true" styleClass="message" errorClass="errors" infoClass="info" id="globalMessages"/>

<div align="center">
     <a:status id="commonstatus"  startText="Request In progress... Please wait..." stopText="" startStyleClass="ajaxmessage"/>
    </div>
    <br/>
   
    <h:form id="quantExperiment" styleClass="edit">
<ui:repeat value="#{quantExperimentHome.reagentForExp}" var="info" >       
  <h:inputText required="true" value="#{info.number}"/>
  ...
</ui:repeat>
  ...
<f:subview xmlns="http://www.w3.org/1999/xhtml"
   xmlns:ui="http://java.sun.com/jsf/facelets"
  xmlns:h="http://java.sun.com/jsf/html"
   xmlns:f="http://java.sun.com/jsf/core"
   xmlns:a4j="http://richfaces.org/a4j"
   xmlns:rich="http://richfaces.org/rich">
    <rich:modalPanel id="panel" width="400" height="120">
     <f:facet name="header">
      <h:panelGroup>
       <h:outputText value="In progress..."></h:outputText>
      </h:panelGroup>
     </f:facet>
     <f:facet name="controls">
      <h:panelGroup>
       <!--<h:graphicImage value="/images/modal/close.png" styleClass="hidelink" id="hidelink"/>-->
       <!--<rich:componentControl for="panel" attachTo="hidelink" operation="hide" event="onclick"/>-->
      </h:panelGroup>
     </f:facet>
     <h:outputText styleClass="info" value="Your request is in progress, please wait..."></h:outputText>
    </rich:modalPanel>
   
    <a4j:commandButton value="Update Experiment" id="update"
   title="Updates the current experiment"
     action="#{quantExperimentHome.update}"
      rendered="#{quantExperimentHome.managed}"
      onclick="this.disabled=true">
     <rich:componentControl for="panel" attachTo="update" operation="show" event="onclick"/>
    </a4j:commandButton>
   
    <a4j:commandButton id="save" title="Creates new experiment for the existing project"
      value="Save Experiment"
     action="#{quantExperimentHome.persist}"
      disabled="#{!quantExperimentHome.wired}"
      rendered="#{!quantExperimentHome.managed}"
      onclick="this.disabled=true">
     <rich:componentControl for="panel" attachTo="save" operation="show" event="onclick"/>
    </a4j:commandButton>
     
</f:subview>
</h:form>