Shopping cart cut off on right side when viewed in Internet Explorer version 7

Market Press works great and looks great with minimal fuss in Firefox and Chrome. Using Internet Explorer Version 7 the shopping cart gets cut off on the right side. I am using the Atahualpa 3.5.3 theme and the classic shopping cart theme. I tried fixing the problem by making the widget area wider in the Atahualpa settings and changing the right padding but that did not help. The website is http://atlasadhesivetape.com

What changes do I need to make?