Pessoal, segue a página completa, de repente assim fica mais fácil de achar o possível problema
<f:view contentType="text/html"/>
<h:form id="frmPage">
<p:growl id="growlMessage" showDetail="false" />
<p:separator/>
<p:panel header="Cadastros - Cliente" footer="XPTO">
<p:toolbar style="background-color:#FFFFFF">
<p:toolbarGroup>
<p:commandButton id="btnShowFilter" icon="ui-icon-zoomin" style="color:#0066FF;background-color:#FFFFFF" ajax="false" actionListener="#{clienteService.consultar}" disabled="#{clienteService.addUpdtState}"/>
<p:commandButton id="btnAtalhos" update="growlMessage" style="color:#0066FF;background-color:#FFFFFF" ajax="false" actionListener="#{clienteService.atalho}" value="Atalhos" disabled="#{clienteService.addUpdtState}"/>
<p:commandButton id="btnAdicionais" update="growlMessage" value="Adicionais" style="color:#0066FF;background-color:#FFFFFF" disabled="#{clienteService.addUpdtState}"/>
<p:separator/>
<p:commandButton id="btnNovo" ajax="false" icon="ui-icon-plusthick" actionListener="#{clienteService.novo}" value="Novo" style="color:#0066FF;background-color:#FFFFFF" disabled="#{clienteService.addUpdtState}"/>
<p:separator/>
<p:commandButton id="btnConsultar" value="Consultar" ajax="false" icon="ui-icon-search" actionListener="#{clienteService.pesquisar}" style="color:#0066FF;background-color:#FFFFFF" disabled="#{clienteService.addUpdtState}"/>
<p:separator/>
<p:commandButton id="btnImprimir" value="Imprimir" icon="ui-icon-print" style="color:#0066FF;background-color:#FFFFFF"/>
</p:toolbarGroup>
<p:toolbarGroup align="right">
<p:commandButton id="btnFecharList" value="Sair do cadastro" ajax="false" style="color:#FF0000;background-color:#FFFFFF" actionListener="#{clienteService.closePage}" icon="ui-icon-closethick" disabled="#{clienteService.addUpdtState}"/>
</p:toolbarGroup>
</p:toolbar>
<p:separator/>
<h:form id="frmGrid" rendered="#{clienteService.addUpdtState}">
<p:panel header="Inserindo/Alterando Cliente">
<h:panelGrid columns="3">
<h:outputLabel for="tfCnpjCpf" value="CNPJ/CPF"/>
<h:inputText id="tfCnpjCpf" value="#{clienteService.cnpjCpf}" maxlength="20" size="20">
<p:ajax event="blur" process="@this" update="@form" onsuccess="alert('OK')" listener="#{clienteService.verificaCpfCnpj}" />
<p:focus/>
</h:inputText>
<h:message for="tfCnpjCpf" errorClass="error"/>
<h:outputLabel for="tfNome" value="Nome"/>
<h:inputText id="tfNome" value="#{clienteService.nome}" maxlength="50" size="50" required="true"/>
<h:message for="tfNome" errorClass="error"/>
<h:outputLabel for="tfFantasia" value="Fantasia" />
<h:inputText id="tfFantasia" value="#{clienteService.fantasia}" maxlength="20" size="20" required="true"/>
<h:message for="tfFantasia" errorClass="error"/>
</h:panelGrid>
</p:panel>
</h:form>
</p:panel>
</h:form>
</html>
No Ajax tentei update="@form", "frmGrid", "formPage" "@all", nada atualiza os outros campos, mais uma vez só atualiza os outros campos quando eu clico no botão Refresh do Browser... Testei no Firefox e Chrome e IE.
Testei com os componentes do JSF bem como os do Primefaces (3.0.1)