Never mind. I figured it out. My surrounding code was a little sloppy, and
wound up invoking this code:
var datepick = new Picker.Date( $$('input.date_toggled'), {
timePicker: false,
positionOffset: {x: 0, y: 4},
pickerClass: 'datepicker',
useFadeInOut: !Browser.ie
});
...multiple times (don't ask). The upshot is multiple pickers were getting
written out. It looks like earlier versions of the picker code only wrote
out one picker per form element, even given my sloppiness. The newer
version is less forgiving...which is my problem. (-;