The #superbox-wrapper and #superbox-container somehow have an offset that pushes them offscreen to the right in IE7. In IE8, Firefox 3.x it displays fine.
This can be fixed by adding left:0; to both the #superbox-wrapper and #superbox-container css styles. It's might be because it was of some conflict with our layout, but I think the fix shouldn't interfere anyway.
Encountered with Superbox 0.9.1, jQuery 1.3.2