Well, we can't have that!
Sounds like a browser or computer problem, rather than your firewall, since the firewall let you download the NASA version. I don't have any flavor of Mac to test for compatibility, so it's always a crap shoot.
I've added a page that provides links to the image that you can use to directly download the images and view them offline in a graphics program: http://rovers.habitablezone.com/Gallery/Spirit/Color/068/BonnePanDirectLinks.html. There's now a link to this page on the Bonneville Panorama page titled "Having problems viewing the images?" to let people get to the direct link page.