soo i have this com bo box inside a custome insert/edit pannel:

 			$kcbTipo = new KoolComboBox("id_tipo");
			$kcbTipo->scriptFolder = $GLOBALS["KoolControlsFolder"]."/KoolComboBox";
			$kcbTipo->styleFolder="default";
			$kcbTipo->itemTemplate = "<div class='column'>{text}</div>";
 			$result = mysql_query("select * from tbl_tipos where id_plantilla=".$_SESSION["id_plantilla"]);
 			
 			$tipoSelectedValue=$_row->DataItem["id_tipo"];
 			if($tipoSelectedValue==null){
				$stmTipos = "select id from tbl_tipos where id_plantilla=".$_SESSION["id_plantilla"] ." and esoportunidad=0";
				$resTipos = mysql_query($stmTipos);
				$rowTipos = mysql_fetch_assoc($resTipos);
				$tipoSelectedValue = $rowTipos["id"];
			}
 			
			while($row = mysql_fetch_assoc($result))
			{
				$kcbTipo->addItem($row["tipo"],$row["id"],null,($tipoSelectedValue==$row["id"])); 
			}

after inserting ot editing everithing seems ok (Record is updated/inserted) but when I click the edit button again, on the console I got this error:

koolform.js:30 Uncaught TypeError: Cannot read property 'firstChild' of null
    at _goFirstChild (koolform.js:30)
    at KoolCombobox.isOpening (koolcombobox.js:720)
    at HTMLDocument.___ (eval at _init (koolcombobox.js:516), <anonymous>:1:35)
_goFirstChild	@	koolform.js:30
isOpening	@	koolcombobox.js:720
___	@	VM4027:1

then everithings seems to be ok but when i got to the koolComboBox i cant choise items from the list with the mouse, only with autocomplete.!!!!!!
What could be causing this ???