I had been running 1.2 of GASP, but then I saw that 1.4.X was conveniently new, so I thought that perhaps a recent update in something else had necessitated a GASP update. Unfortunately, 1.4.X did not fix the problem.
The only thing that I have changed myself on the site (not including various plugin updates and such) is some widget text. But I both removed that widget and also reverted it, and neither attempt fixed the problem.
At a loss to explain what happened.