求教火狐上的getElementsByTaName()无效！

-------------------<js>
JScript code

        function checkAddOrganIdExists(organId){
                        if(organId==""||organId==null){
                           failedDiv(document.getElementById("divCheckOrganIdResult"),"部门ID不能为空！");
                           return ;
                        }
                       ajaxChecking = true;
                       var ajaxUrl = 'organAction!checkOrganIdExists.action?organId='+organId+'&time='+(new Date().getTime());
                       $.get(ajaxUrl, {Action:"get",Name:"fortune"}, function (data, textStatus){

                           var checkResultNodes = data.documentElement.getElementsByTagName("result");
                           if(checkResultNodes[0].text=="true"){
                               failedDiv(document.getElementById("divCheckOrganIdResult"),"该ID已经存在，不能使用！");                      
                               ajaxCheckOrganExists = true;
                           }else{
                               successDiv(document.getElementById("divCheckOrganIdResult"),"检查无误");
                               ajaxCheckOrganExists =false;
                           }
                           //alert(textStatus);//请求状态：success，error等等。
                           //alert(this);
                           ajaxChecking = false;
                           });
                   }

-------------------------------<xml>
XML code

<organ-check-exists id="checkOrgan" >
    <result><s:property value="organExists"/></result>
</organ-check-exists>

在IE中一切正常，但在火狐中不管怎样只执行else中的方法!

JScript code

//if(checkResultNodes[0].text=="true")
//====>
if(checkResultNodes[0].firstChild.nodeValue=="true"){
                               failedDiv(document.getElementById("divCheckOrganIdResult"),"该ID已经存在，不能使用！");                      
                               ajaxCheckOrganExists = true;
                           }else{
                               successDiv(document.getElementById("divCheckOrganIdResult"),"检查无误");
                               ajaxCheckOrganExists =false;
                           }