I managed to solve this issue on gowalla and stackoverflow (it happens to the footer) by adding a min-width to the body element. I think that on your own site though, it would be better to apply it to a wrapper div that encompasses ALL of the page's content (including the footer).
You will need to set it's value to the minimum fixed width of the content, so if your main content div is set to be 960px wide, then that's probably what you want (but you may need to tweak to account for extra margins/borders etc).
Here's an example: http://jsfiddle.net/qUyp2/
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