Erro ao sobreescrever ArrayList! Pq?

List<Menu> listaMenu = (List<Menu>) menuDAO.todosPorMunic(municipio.getId());

public class MunicipioController {

	private Municipio municipio ;
	private MunicipioDAO municipioDAO;
	private Menu menu;
	private MenuDAO menuDAO;
	private SubmenuDAO submenuDAO;
	private boolean renderizador;
	private String htmlOut = "";
	
	public MunicipioController(){
		setRenderizador(false);
	}
	
	public String listar(){
		//setRenderizador(true);
		municipio = new Municipio();
		
		try {
			municipioDAO = new MunicipioDAO();
			menuDAO = new MenuDAO();
			submenuDAO = new SubmenuDAO();
			
			municipio = (Municipio) municipioDAO.procurar(1);
			
			htmlOut += municipio.getId();
			
			List<Menu> listaMenu = new ArrayList<Menu>();
			listaMenu = (List<Menu>) menuDAO.todosPorMunic(municipio.getId());
			
			
			for(int i = 0; i < listaMenu.size(); i++){
				
				menu = new Menu();
				
				menu = listaMenu.get(i);
				
				htmlOut += menu.getId();
				
				List<Submenu> listaSubmenu = submenuDAO.todosPorMenu(menu.getId());
				
				for(int j = 0; j < listaSubmenu.size(); j++){
					Submenu sub = new Submenu();
					sub = listaSubmenu.get(j);
					
					htmlOut += sub.getTitulo();
					System.out.println(sub.getTitulo());
				}
			}
			
			System.out.println("OK "+htmlOut);
			
		} catch (DAOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			System.out.println("erro"+e.getMessage());
		}
		
		return null;
	}

	public List<Municipio> getMunicipios(){
		try {
			municipioDAO = new MunicipioDAO();
			return (List<Municipio>) municipioDAO.todos();
		} catch (DAOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return null;		
	}
	public void setMunicipio(Municipio municipio) {
		this.municipio = municipio;
	}


	public Municipio getMunicipio() {
		return municipio;
	}


	public void setRenderizador(boolean renderizador) {
		this.renderizador = renderizador;
	}


	public boolean isRenderizador() {
		return renderizador;
	}

	public void setHtmlOut(String htmlOut) {
		this.htmlOut = htmlOut;
	}

	public String getHtmlOut() {
		return htmlOut;
	}

	public void setMenu(Menu menu) {
		this.menu = menu;
	}

	public Menu getMenu() {
		return menu;
	}

	public void setMenuDAO(MenuDAO menuDAO) {
		this.menuDAO = menuDAO;
	}

	public MenuDAO getMenuDAO() {
		return menuDAO;
	}
}

public List<Submenu> todosPorMenu(int menuid) throws DAOException {
		// TODO Auto-generated method stub
		
		PreparedStatement ps = null;
        Connection conn = null;
        ResultSet rs = null;

        try {
            conn = this.conn;
            ps = conn.prepareStatement("select titulo from submenu where menu ="+ menuid);
            rs = ps.executeQuery();
            
            List<Submenu> list = new ArrayList<Submenu>();
            
            while (rs.next()) {
            	
                Submenu submenu = new Submenu();

                submenu.setTitulo(rs.getString(1));
                
                list.add(submenu);

            }
            return list;

        } catch (SQLException sqle) {
        	sqle.printStackTrace();
            throw new DAOException(sqle);
        } finally {
            ConnectionFactory.closeConnection(conn, ps, rs);
        }
	}

Erro:

Caused by: org.postgresql.util.PSQLException: Um erro de E/S ocorreu ao enviar para o processo servidor.

at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:220)

at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:451)

at org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:350)

at org.postgresql.jdbc2.AbstractJdbc2Statement.executeQuery(AbstractJdbc2Statement.java:254)

at idesp.sie.dao.SubmenuDAO.todosPorMenu(SubmenuDAO.java:190)

… 38 more

Caused by: java.io.IOException: Stream closed

at sun.nio.cs.StreamEncoder.ensureOpen(Unknown Source)

at sun.nio.cs.StreamEncoder.flush(Unknown Source)

at java.io.OutputStreamWriter.flush(Unknown Source)

at org.postgresql.core.PGStream.flush(PGStream.java:507)

at org.postgresql.core.v3.QueryExecutorImpl.sendSync(QueryExecutorImpl.java:692)

at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:193)

… 42 more

erroorg.postgresql.util.PSQLException: Um erro de E/S ocorreu ao enviar para o processo servidor.

...
            List<Submenu> listaMenu = menuDAO.todosPorMunic(municipio.getId());   
               
               
            for(int i = 0; i < listaMenu.size(); i++){   
                   
                menu = listaMenu.get(i);//se for o caso force o cast aqui 
    ...