Craig, do you know whether I am correct that updates are "rolled out" (translation: forced on users) on the 6th of every month? If that is the case, then the timing of this problem's onset strongly points to the latest release.

I wonder too whether all users get the updates at the same time. As I mentioned above, my daughter tested it for me last week and reported that her attachment opened in Adobe Reader, and the Save dialog also popped up. I wish I could determine whether we are both on the same release.