Interesting. But it's only sort of broken.
The image swaps are still working after I tried the map quest window-- the
page still re-sized itself for the taller images. But, for whatever reason,
the image wasn't displayed. For the page to resize, though, it had to be able
to find the image to get the size information.
In addition, I was only able to reproduce this behavior in IE6, and when I
refreshed the page, it behaved normally again. When I tested your page under
Opera and Mozilla, the image swaps were unaffected. This may be related to the
IE6 bug that causes a page to not redraw properly under certain situations. I
don't remember any of the other situations.

But I have a page where I use
the "max-width" hack. You specify max-width:800px (or whatever) for the other
browsers, then use width:expression(document.body.clientWidth > 800? "800px" :
"auto") to make IE6 behave as though it supported max-width. (IE is the only
browser that recognizes "expression".) When using this workaround, if you have
the page maximized in IE, then reduce the size of your browser window, the page
will become blank until you refresh. Then it behaves normally.
So, it's a render bug of some sort. There might be a script alteration to fix
it, but I don't know of any.