One of the PMs received an email notification that the doc has been posted. He clicked on each image link embedded in the notification. Of the four links, one gave him a "not authorized" message. The rest displayed as expected. He was using FF on a Mac. The third image in the doc is the one that generated the error.
I asked another team mate to try the same links. He saw the "not authorized" error on the first image. The other three displayed with no problem. He was also using FF on a Mac.
I was able to view all images from the email links on FF on Windows 7 as was another teammate on FF on Windows 8.