Moreover, when the error occurs, both date pickers are inoperable, even after the interface is updated. However, I have excised the code in the Shown event that updates the date pickers and the error still occurs. Since the Shown event is firing, my code might in principle have been at fault. (How it is that some parts of the user interface get updated and others don’t is still a mystery, though.)

This also explains why displaying the Javascript Console fixed things: it unfroze the client so that the results of the Shown event could be displayed. I moved the tab order of the date pickers after the listbox, and now the listbox always gets updated with data that only the Shown event can create. I believe that the Shown event actually is firing on the server, but the user interface on the client is frozen after the error occurs, so the label text that I had set up to indicate that the event was firing never got updated, making it appear that the event didn’t fire. However, things are more complicated than I thought. Neither are operable: if you click on them, nothing happens. The second one is always set to the present day, no matter what the initial date was. I have two date-time pickers, and when the error occurs, the first one in tab index order remains set to the initial date supplied in the inspector. The error occurs whether the initial date is blank or whether I set it to a particular SQLDate.

Sorry Greg, I misinterpreted what you meant.

Xojo msgbox not show up on web page