smjjames, the issue is almost certainly that your browser has that page cached and is showing you an outdated view of the preview. I have checked our Previews Page in every major browser in both Windows and Mac, including Firefox, Google Chrome, Opera and Internet Explorer for Windows, and the progress bar displays correctly in every case.

All modern browsers cache Web pages to improve performance, but sometimes that can cause outdated information to be displayed. The only way to ensure that you have the latest information and images for a given Web page is to update your browser's cache (either by clearing it, and then reloading the page), or by manually refreshing the contents of the page by using your browser's reload/refresh function (in Firefox, there's a button for that or you can click View=>Reload to refresh the page).