invalid pointer in window.showModalDialog using javascript please help

[lianqtlit]

please help!!!!

i have this var xmltreeA.

xmlTreeA = "<TREENODES>
<TREENODE ID='4' TEXT='&lt;acronym title=\"res_cbiRFModuleGI\"&gt; res_cbiRFModuleGI &lt;/acronym&gt;' imageUrl='../../images/Maintenance/MAINGI.gif' sNavigateFlag = '0'>
<TREENODE ID='20' TEXT='&lt;acronym title=\"System - Masters\"&gt; System - Masters &lt;/acronym&gt;' imageUrl='../../images/Maintenance/MAINGI.gif' navigateUrl= 'javascript: GetAssembly%28%27SysGIMasters%27%2C%270%27%2C%27%27%29' sNavigateFlag = '0'>
</TREENODE>
<TREENODE ID='21' TEXT='&lt;acronym title=\"System - Companies\"&gt; System - Companies &lt;/acronym&gt;' imageUrl='../../images/Maintenance/MAINGI.gif' navigateUrl= 'javascript: GetAssembly%28%27SysGICompanies%27%2C%270%27%2C%27%27%29' sNavigateFlag = '0'>
</TREENODE>
<TREENODE ID='22' TEXT='&lt;acronym title=\"System - Servers\"&gt; System - Servers &lt;/acronym&gt;' imageUrl='../../images/Maintenance/MAINGI.gif' navigateUrl= 'javascript: GetAssembly%28%27SysGIServers%27%2C%270%27%2C%27%27%29' sNavigateFlag = '0'>
</TREENODE>
</TREENODES>"

my code

var sTrvMenuSet = top.frmNav.frames[2].frames[1].document.forms[0].all("q_TrvMenuSet");

var xmlTreeA = sTrvMenuSet.treeNodeSrc;

sUrl = "../Dialogs/EditMyFavouritesShell.aspx?sID="+ sID +"&sSelectedMenu="+ sSelectedMenu +"&sItemIds="+ sItemIds +"&bSystemSelected="+ bSystemSelected +"&sFormTitle="+ sFormTitle +"&sFontSize="+ sCboFontSize +"&sXmlTree="+ xmlTreeA;

var dialogProps = "dialogWidth:523px;dialogHeight:353px;dialogLeft=310;dialogTop=310;help=no;scroll=no;status=no;";

var oRetObject = window.showModalDialog(sUrl,"edit",dialogProps);


im encountering an error called invalid pointer in this code
var oRetObject = window.showModalDialog(sUrl,"edit",dialogProps);