Intermittent Internet Explorer Error whilst using Javascript to traverse XML Nodes

Question

Hi there all,

Basically I use a javascript SOAP plugin to send and receive XML from a web service.

Recently I've been experiencing intermittment (1 in every 20-30 times) errors in IE when trying to access data in the XML file.

Bear with me on this, I'm going to try and go into a fair amount of detail to help anyone who is willing to read this:

I have a html file, with an external javascript file attached.

In the javascript file I include 5 global variables:

var soapRes;
var questionXML;
var xRoot;
var assessnode;
var edStage = 0;

Once the html file is at a readystate I request the XML file from the web service like this:

function initNextStage(strA) {

    // Set pl Parameters here
    var pl = new SOAPClientParameters();
// soap call   
 var r = SOAPClient.invoke(url, "LoadAssessment", pl, true, initStage_callBack);

}

function initStage_callBack(r, soapResponse)
{    

soapRes = soapResponse;

initvalues();

function initvalues(){

xRoot = soapRes.documentElement;

assessnode = xRoot.getElementsByTagName("ed")[0];

questionXML = assessnode.getElementsByTagName("question")[edStage];    


}

}

Once this is completed the XML should be loaded into memory via the global variable soapRes.

I then save values to the XML before moving one node down the XML tree, and pulling the next set of values out of it.

function submitAns1() {

var objAns;
var corElem;
var corElemTxt;
questionXML = assessnode.getElementsByTagName("question")[edStage];    
objAns = questionXML.getElementsByTagName("item")[0].getAttribute("answer");

corElem = soapRes.createElement("correct");
corElemTxt = soapRes.createTextNode("value");
questionXML.appendChild(corElem);
corElem.appendChild(corElemTxt);

if(objAns == "t") {

corElemTxt.nodeValue = "true";

    }

else {

corElemTxt.nodeValue = "false";

}

edStage++;

questionXML = assessnode.getElementsByTagName("question")[edStage];    

var inc1 = questionXML.getElementsByTagName("sentence")[0];

var inc2 = questionXML.getElementsByTagName("sentence")[1];

var edopt1 = questionXML.getElementsByTagName("item")[0];

var edopt2 = questionXML.getElementsByTagName("item")[1];

var edopt3 = questionXML.getElementsByTagName("item")[2];

var edopt4 = questionXML.getElementsByTagName("item")[3];

var edopt5 = questionXML.getElementsByTagName("item")[4];

var temp1 = edopt1.childNodes[0].nodeValue;
var temp2 = edopt2.childNodes[0].nodeValue;
var temp3 = edopt3.childNodes[0].nodeValue;
var temp4 = edopt4.childNodes[0].nodeValue;
var temp5 = edopt5.childNodes[0].nodeValue;

    }

This is an example of our XML:

<ed>
<appid>Administrator</appid>
<formid>ED009</formid>
<question id="1">
<sentence id="1">[email protected]</sentence>
<sentence id="2">[email protected]</sentence>
<item id="0" answer="f" value="0">0</item>
<item id="1" answer="f" value="1">1</item>
<item id="2" answer="f" value="2">2</item>
<item id="3" answer="t" value="3">3</item>
<item id="4" answer="f" value="4">4</item>
</question>
<question id="2">
<sentence id="1">Beausdene 13</sentence>
<sentence id="2">Beauscene 83</sentence>
<item id="0" answer="f" value="0">0</item>
<item id="1" answer="f" value="1">1</item>
<item id="2" answer="t" value="2">2</item>
<item id="3" answer="f" value="3">3</item>
<item id="4" answer="f" value="4">4</item>
</question>
</ed>

The error I receive intermittently is that "questionXML" is null or not an object.

Specifically this line when I call on the submitAns1() method:

 questionXML = assessnode.getElementsByTagName("question")[edStage];

This solution works on FF, Opera, Chrome & Safari without any issues as far as I am aware.

Am I accessing the XML nodes incorrectly? I've been toying with fixes for this bug for weeks now, I'd really appreciate any insight into what I'm doing wrong.

On a side note, this is a personal project of mine - it's not university related - I'm much too old for that!

Any help greatly appreciated.

Regards,

Sykth.