Problemas com JSF 2.0 (<h:selectOneMenu> e <f:ajax>)

<h:outputLabel value="Especialidade: " for="consulta-especialidade" />
		<h:selectOneMenu id="consulta-especialidade"
			value="#{consultaBean.especialidadeId}">
			<f:ajax event="change"  render="consulta-medico" listener="#{consultaBean.listenerMedicosByEspecialidade}" />						
			<f:selectItem itemLabel="Selecione..." itemValue="" />
			<f:selectItems value="#{especialidadeBean.listaEspecialidades}"
				var="esp" itemLabel="#{esp.descricao}" itemValue="#{esp.id}" />
		</h:selectOneMenu>
		<p:message for="consulta-especialidade" />


		<h:outputLabel value="Médico: " for="consulta-medico" />
		<h:selectOneMenu id="consulta-medico" value="#{consultaBean.medicoId}">

			<f:selectItem itemLabel="Selecione..." itemValue="" />
			<f:selectItems value="#{consultaBean.listaMedicosByEspecialidade}"
				var="medByEsp" itemLabel="#{medByEsp.nome}" itemValue="#{medByEsp.id}" />				 
		</h:selectOneMenu>
		<p:message for="consulta-medico" />

   <h:commandButton value="Salvar">
			<f:ajax event="click" execute="consulta-convenio consulta-medico consulta-paciente consulta-data"
				listener="#{consultaBean.salvar}" render="@form" />
		</h:commandButton>

public void listenerMedicosByEspecialidade(AjaxBehaviorEvent event) {	
		listaMedicosByEspecialidade = ServiceFactory.getInstance().getMedicoService().findByEspecialidade(entityManager, especialidadeId);
	}

	public List<Medico> getListaMedicosByEspecialidade() {
		return listaMedicosByEspecialidade;
	}

	public void setListaMedicosByEspecialidade(
			List<Medico> listaMedicosByEspecialidade) {
		this.listaMedicosByEspecialidade = listaMedicosByEspecialidade;
	}
	public Integer getMedicoId() {
		return medicoId;
	}

	public void setMedicoId(Integer medicoId) {	
		this.medicoId = medicoId;
	}

package com.prontuario.filter;

import java.io.IOException;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class JPAFilter implements Filter {

	private EntityManagerFactory factory;

	@Override
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {

		EntityManager entityManager = this.factory.createEntityManager();
		request.setAttribute("entityManager", entityManager);

		entityManager.getTransaction().begin();

		chain.doFilter(request, response);

		try {
			entityManager.getTransaction().commit();
		} catch (Exception e) {
			entityManager.getTransaction().rollback();
			throw new ServletException(e);
		} finally {
			entityManager.close();
		}
	}

	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		this.factory = Persistence.createEntityManagerFactory("prontuario");
	}

	@Override
	public void destroy() {
		this.factory.close();
	}

}

@ManagedBean  
    public class ConsultaBean {  
      
        @ManagedProperty(value = "#{entityManager}")  
        private EntityManager entityManager;  
        private Consulta consulta = new Consulta();  
      
        private List<Consulta> listaConsultas;  
      
          
        public EntityManager getEntityManager() {  
            return entityManager;  
        }  
      
        public void setEntityManager(EntityManager entityManager) {  
            this.entityManager = entityManager;  
        }  
      
      
        public Consulta getConsulta() {  
            return consulta;  
        }  
      
        public void setConsulta(Consulta consulta) {  
            this.consulta = consulta;  
        }  
      
        public List<Consulta> getListaConsultas() {  
            if (listaConsultas == null) {  
                listaConsultas = ServiceFactory.getInstance().getConsultaService().findAll(entityManager);  
            }  
            return listaConsultas;  
        }  
      
      
      
          
        public void salvar() {  
              
            ServiceFactory.getInstance().getConsultaService().insert(entityManager, consulta);  
            consulta = new Consulta();  
            listaConsultas = null;  
        }  
      
        public void remover(Consulta consulta) {  
            ServiceFactory.getInstance().getConsultaService()  
                    .delete(entityManager, consulta);  
            listaConsultas = null;  
        }  
      
    }