Today at work we were dealing with Javascript that popped up a Calender widget. For some reason, on one particular page the calender would appear underneath some of the other widgets on the page.
It turns out that any absolute div in IE that is meant to be on top of a drop down list will have the drop down list on top of the absolute. Note: text input fields, multiline text input fields, etc, do -not- appear on top of the absolute. This is correct behaviour. Why the drop down list feels it should be on top is beyond me.
The following html did it for me:
<html>
<body>
<div style="position: absolute; background-color: blue; width: 100px; height: 100px">This is a test</div>
<select name="foo"></select>
</body>
</html>