Preencher um ComboBox RichFaces com dados do Banco

Bom dia ,

Estou tentando popular um comboBox do RichFaces , mas estou tendo problemas , a query é realizada normalmente mas da um erro de cast.

veja o codigo abaixo :

public List<SelectItem> atualizaComboCidade() {

        itensCidades = new ArrayList<SelectItem>();
        ceps = (List<Cep>) todosResultItensCidades();
       
        for (Cep e : ceps) {
            itensCidades.add(new SelectItem(new String(e.getCidade())));
        }

        setCi(true);
        return itensCidades;

    }

    private List<?> todosResultItensCidades() {

        Map<String, Object> params = new HashMap<String, Object>();
        params.put("uf", uf);

        return cepDao.listPesqParam(consultaCidades(), params);

    }

    private String consultaCidades() {
        String query = "SELECT " +
                " DISTINCT(c.cidade) FROM Cep c " +
                " WHERE c.uf = :uf";

        return query;
    }


  Trecho do codigo Xhtml


<h:outputText  styleClass="rich-label" value="Selecione o Estado" />
                            <rich:comboBox  size="2" label="UF" defaultLabel="UF" id="uf" required="true" value="#{rotaController.uf}" >
                                <f:selectItem itemValue="AC"/>
                                <f:selectItem itemValue="AL"/>
                                <f:selectItem itemValue="AM"/>
                                <f:selectItem itemValue="AP"/>
                                <f:selectItem itemValue="BA"/>
                                <f:selectItem itemValue="CE"/>
                                <f:selectItem itemValue="DF"/>
                                <f:selectItem itemValue="ES"/>
                                <f:selectItem itemValue="GO"/>
                                <f:selectItem itemValue="MA"/>
                                <f:selectItem itemValue="MG"/>
                                <f:selectItem itemValue="MS"/>
                                <f:selectItem itemValue="MT"/>
                                <f:selectItem itemValue="PA"/>
                                <f:selectItem itemValue="PB"/>
                                <f:selectItem itemValue="PE"/>
                                <f:selectItem itemValue="PI"/>
                                <f:selectItem itemValue="PR"/>
                                <f:selectItem itemValue="RJ"/>
                                <f:selectItem itemValue="RN"/>
                                <f:selectItem itemValue="RO"/>
                                <f:selectItem itemValue="RR"/>
                                <f:selectItem itemValue="RS"/>
                                <f:selectItem itemValue="SC"/>
                                <f:selectItem itemValue="SE"/>
                                <f:selectItem itemValue="SP"/>
                                <f:selectItem itemValue="TO"/>
                                <f:validateLength minimum="2" maximum="2"  />
                               <a4j:support event="onchange" action="#{rotaController.atualizaComboCidade}" reRender="comboCidade"/>
                            </rich:comboBox>

                            <a4j:commandButton value="update" reRender="comboCidade"/>
                            <h:outputText  styleClass="rich-label" id="lbcidade"  rendered="#{rotaController.ci == true}"   value="Selecione a Cidade:" />
                            <rich:comboBox  id="comboCidade" rendered="#{rotaController.ci == true}"  value="#{rotaController.cidade}"
                                            defaultLabel="Selecione a Cidade..." required="true" >
                                <f:selectItems value="#{rotaController.itensCidades}"/>
                                <a4j:support event="onchange"
                                             ajaxSingle="true" reRender="bairro" />
                            </rich:comboBox>