jquery ajax issues

I have a problem that is as follows:

In my system I have a combo that serves as a parameter to load (via ajax) a second combo, this works normally.

Then, when clicking on an item in a table, the first combo is updated and based on the selected combo item it loads a second combo.

But it does not work!

I have already used jquery on / live / bind, but it does not work

follow the code:

$ ('. tableLineCargo'). live ('click', fillFormularioCargo); $ ('# responsavelcombo'). on ('change', listAlvos);

    function listarAlvos(){
      var dados = {
        acao: 'combo',
        nome: alvo
      };

      var vurl;
      var respcombo = $('#responsavelcombo').val();

      if (respcombo == 0){
        $('#alvocombo').html("");
      }else{
        if (respcombo == 1){vurl = 'associacaocrud.php';}
        if (respcombo == 2){vurl = 'grupocrud.php';}
        if (respcombo == 3){vurl = 'regiaocrud.php';}
        if (respcombo == 4){vurl = 'templocrud.php';}

        $.ajax({
          url: vurl,
          type: 'POST',
          data: dados,
          success: function(retorno){
            $('#alvocombo').html(retorno);           
          }
        });
      }
    };