My site is here. Unfortunately, I can't share the link to the previous page that sends things awry because it's behind a corporate firewall.
This is what it looks like initially:
But after visiting the other page and then retyping the URL, I see this:
It looks as if the margin and/or padding after the H1 element has increased, meaning that the header DIV grows taller than the height it is supposed to be.
The exact version of IE where this happens is 8.0.7601.17514.
Hope that helps! Clues welcome (and although I can't see why one page should affect another, maybe there is a simple CSS fix). I'm not keen on absolute positioning, but am struggling to find a way to get the footer as I want it without using absolute on the DIVs.