dhtmlxCombo not initializing in autocomplete mode

Hi, I have this issue. I cannot initilize Combobox in autocomplete mode. It throws this error:

parent.style is undefined.

This is the javascript code:

   var combo_grupos = {
	    parent: "combo_grupos",
	    width: 200,
	    filter: "../connectors/complete_grupos_relacionador.php"
	var z = new dhtmlXCombo(combo_grupos);

This is HTML code:

<div id="combo_grupos" style="width:200px; height:30px;"></div>

I am doing like doc but I fail. Combobox is in a layout, but i dont think this is important.

Try to write :

var z = new dhtmlXCombo("combo_grupos");

“combo_grupos” - is a string