IE5中用JavaScript跨frame加option问题

跨frame加option，以下代码在IE5中会出错，但在IE4、IE6、Opera6、NNx中都没有问题：

<script>function addOption(aSelect, optionId, optionName) {    newOption = new Option(optionName, optionId);    aSelect.options[aSelect.options.length] = newOption;}</script>

<script>function addOption(aSelect, optionId, optionName) {    ownerWindow = aSelect.document.parentWindow;    ownerWindow.newOption = new Option(optionName, optionId);    aSelect.options[aSelect.options.length] = ownerWindow.newOption;}function crossFrameAddOption() {    var aSelect = parent.otherFrameName.document.forms[0].theSelectName;    addOption(aSelect , "id"+ aSelect.options.length, "name"+ aSelect.options.length);}</script><input type="button" onClick="crossFrameAddOption();" value="test">