3.5.1 losing new widget areas

I installed 3.5.1 on a site where 3.4.6 had been running. I had one new widget area. I didn't notice at first, but the new widget area was lost in the process. I had to put it in the Above the Loop area of the center column, visit the front page, and then it showed up in the New Widget Area creation section, as well as in Appearance/Widgets. The text widget inside it was also there at that point.