JNDI Datasource in tomcat

Hi

        Im trying to get a connection through a JNDI service in tomcat.
        Im
        trying wuth this config.

        <Resource
                auth="Container"
                name="jdbc/openbravo"
                type="org.postgresql.jdbc3.Jdbc3SimpleDataSource"
                driverClassName="org.postgresql.Driver"
                password="postgres"
                maxIdle="5"
                maxWait="10000"
                user="postgres"
                maxActive="20"
                databaseName="openbravo"
                serverName="127.0.0.1"
                portNumber="5432"
                factory="org.postgresql.jdbc3.Jdbc3ObjectFactory"/>

        using thi driver. pg74.216.jdbc3.jar
        I get this error
        - org.postgresql.util.PSQLException: A result was returned when
        none was
        expected.
        - Unable to create a connection pool
        org.openbravo.exception.PoolNotFoundException: Failed when
        creating
        database connections pool: org.postgresql.util.PSQLException: A
        result
        was returned when none was expected.

        Here
         Context initctx = new InitialContext();
         Context ctx = (Context) initctx.lookup("java:/comp/env");
         DataSource ds = (DataSource) ctx.lookup(jndiResourceName);
        con = ds.getConnection();
        -- Here i get a org.postgresql.jdbc3.connectionjdbc3
         PreparedStatement pstmt =
        con.prepareStatement(dbSessionConfig);
        pstmt.executeUpdate();  <--- Here a got the error

        when i used the driver manager with this driver
        jdbc3-postgresql.jar i
        think that i got another kind of connection and i havent got no
        error.
        seems that now i have a config error but i dont really know
        whats the
        correct way to fix it

        can someone help me

        Thanks and regards