表单提交时出现javascript错误“htmlfile：访问被拒绝”

Question

当用户在IE8中通过javascript命令form.submit从“onbeforeunload”的事件处理程序调用来关闭我的模态网页窗口时尝试回发时，我收到错误“htmlfile：Access is denied” 。 该怎么办？

<script language='javascript' for='window' event='onbeforeunload()'>
if (this.event.clientY<0){__doPostBack('__Page','__close')}
</script>

<script type="text/javascript">
<!--
var theForm = document.forms['MyModalForm'];
if (!theForm) {
theForm = document.MyModalForm;
}
function __doPostBack(eventTarget, eventArgument) {
if (!theForm.onsubmit || (theForm.onsubmit() != false)) {
    theForm.__EVENTTARGET.value = eventTarget;
    theForm.__EVENTARGUMENT.value = eventArgument;

    theForm.submit();//ERROR: Access is denied  !!!!!!!!!!!!!!

}
}
// -->
</script>    

我使用的是windows7，iis7.5，asp.net4.0。

感谢。