Hi Craig,
Yes, I think we get stuck with the double scroll-bar in =< IE7 using the overflow method, so it's probably a case of best possible scenario using overflow in Mozilla and IE8 and using a conditional <!--[if lte IE 7]> in your page headers to an alternative stylesheet for the rest.
But your page looks and works fine for me without the overflow at all, so I'm not sure what is happening at your end!