Hi,
I looked at your site using IE 8 mode in IE 9 and I was able to replicate the problem on your site. However, I have no idea how to solve the problem. It looks to me like it has something to do with the javascript you are using to scroll the side content down the page. You have a lot of extra javascript on that page, fancybox, stickyfloat, movingboxes etc. Some of that may not even be used on this specific page. I guess you have that javasvcript in layout.master and some of it is not really used on every page. I would try copying your skin with a new name, assign the copy to that page so it is not using the same skin as the rest of the site (you can enable per page skins in site settings, then a skin dropdown will appear in page settings). Remove any javascript from that page that is not used. If the problem persists then try removing more javsascript until the problem goes away to identify for sure which javasdcript is causing it. My best guess is that it is caused by that stickyfloat.js or whatever script is doing the scrolling on the side content.
Wish I could be more helpful but that is all I have for you. The problem is not reproducible on the demo site or my local machine so it must be something with all that extra javascript you have.
Best,
Joe