I opened form-output.php and changed
input type="date" name="vfb-%1$d" id="%2$s" value="%3$s" class="vfb-text vfb-date-picker %4$s %5$s %6$s"
to input type="text" name="vfb-%1$d" id="%2$s" value="%3$s" class="vfb-text vfb-date-picker %4$s %5$s %6$s"
That seems to have fixed the problem.
I also disabled the plugins, and even changed the theme to twentyten, and the date picker still didn’t work. It was working fine until I made the latest WordPress update.
