The problem appears to be caused by the javascript in the iframe trying to access its parent to resize the iframe. This works on launchpad, because the page with the iframe and the page inside the iframe are on the same domain name; therefore, the browser doesn't trigger a security error. This was not obvious in Firefox with Firebug, but there was a clear security error when testing it in Safari 4.
The problem appears to be caused by the javascript in the iframe trying to access its parent to resize the iframe. This works on launchpad, because the page with the iframe and the page inside the iframe are on the same domain name; therefore, the browser doesn't trigger a security error. This was not obvious in Firefox with Firebug, but there was a clear security error when testing it in Safari 4.