Ajax Loading Box will not unload when clicking any file link

In my store, if you click a link that downloads a file (such as http://mydomain.com/downloads/coolfile.zip), the “Loading” box appears and won’t go away. Of course, you can click “refresh” and continue happily along, but that is not obvious. Users basically do nothing, waiting for the “loading” box to disappear, which it will never do.

Problem occurs in both custom skin and “out of the box” skin (austere), Firefox and Safari (haven’t tried IE), on both test server and live server, with more than one type of link, etc. It doesn’t occur in CS-Cart demo store, so I turned off any addons that demo store had off, still no joy.

Any thoughts on how to solve this, or even more troubleshooting ideas?