vBulletin Javascript issue in IE

[Snakehill]

This is a piece of code I created as a cross-brower/cross-platform solution for fixing/locking a div on a custom vB page (so that it scrolls along with the page scrolling). However, when adding it, it works in all browsers but IE. Unlike the other ones, Internet Explorer cannot seem to get hold of any of the values requested by the code, and required for it to work well. Other functions still work, it is just not getting the offsetTop and window.pageYOffset values.

However, when trying this outside of a vB page, it works great, even on IE, so something from vB seems to be conflicting and I have no idea what it is or how to make it work along with this code.

<script type="text/javascript">
window.onscroll = function (e) {
var basediv = document.getElementById('basediv').offsetTop;
var setdiv = document.getElementById('setdiv');
 if (window.pageYOffset	< (basediv - 1)) {
 setdiv.style.top = "0px";
 } 
 else {
 setdiv.style.top = (1 + (window.pageYOffset - basediv) + "px");
 }
}
</script>

The offsetTop and window.pageYOffset for some reason always return 0 and undefined. I have tried adding the code anywhere on the page, in between the head tags, and in an external js file, but nothing worked.

The following I have used to test it:

<script type="text/javascript">
window.onscroll = function (e) {
var testdiv = document.getElementById('testdiv').offsetTop;
alert(window.pageYOffset + " " + testdiv);
}
</script>

<div id="testdiv"></div>

Again, it works fine on its own but as soon as it is placed on a custom vB page, something stops it from getting the requested values.

Help is very much appreciated! Thanks!