vs2005页面调用jQuery在IE8报：对象不支持此属性或方法

如题，<link rel="stylesheet" href="demoStyle/demo.css" type="text/css"/>
  <link rel="stylesheet" href="ztreeStyle/ztreeStyle.css" type="text/css"/>
  <script type="text/javascript" src="jquery-1.4.2.js"></script>
  <script type="text/javascript" src="jquery.ztree-2.6.js"></script>
  <script type="text/javascript" src="asyncData/demoData.js"></script>
  <script type="text/javascript" src="demoTools.js"></script>
  <script language="JavaScript">
var ztree1, ztree2;
var setting; setting = {
editable: true,
edit_renameBtn:false,
edit_removeBtn:false,
dragCopy: true,
dragMove: true,
callback: {
click: ztreeOnClick,
drop: ztreeOnDrop
}
}; $(document).ready(function(){
reloadtree();
}); var preSelectedNode1;
var preSelectedNode2; function ztreeOnClick(event, treeId, treeNode) {
if (treeId=="treeDemo") {
if (preSelectedNode1 == treeNode) {
ztree1.cancelSelectedNode();
preSelectedNode1 = null;
} else {
preSelectedNode1 = treeNode;
}
} else {
if (preSelectedNode2 == treeNode) {
ztree2.cancelSelectedNode();
preSelectedNode2 = null;
} else {
preSelectedNode2 = treeNode;
}
}
} function ztreeOnDrop(event, treeId, treeNode, targetNode, moveType) {
preSelectedNode1 = ztree1.getSelectedNode();
preSelectedNode2 = ztree2.getSelectedNode();
} function movetreeL2R() {
movetreeNode(ztree1, ztree2);
}

function movetreeR2L() {
movetreeNode(ztree2, ztree1);
}

function movetreeNode(srctree, targettree) {
var srcNode = srctree.getSelectedNode();
if (!srcNode) {
alert("请先选择需要移动的节点！");
return;
}
var targetNode = targettree.getSelectedNode();
srctree.removeNode(srcNode);
targettree.addNodes(targetNode, [srcNode]);
targettree.selectNode(srcNode);
} function reloadtree() {
ztree1 = $("#treeDemo").ztree(setting, zNodes);
ztree2 = $("#treeDemo2").ztree(setting, zNodes);
}
  </script>在这一行ztree1 = $("#treeDemo").ztree(setting, zNodes);报对象不支持此属性或方法，请高手解答，谢谢。