I don't think this will be a quick fix as you have all sorts of margins and padding affecting the layout, including column wrappers set to 150px but are pushed out to 200px.. IE8 and firefox appear ok, so you could use IE7 conditional comments to "fix" things. If it were my site I would change most layout settings (widths/margins and padding) to get everything showing consistant in all browsers.

ps.. I do like the look of your site.