I don't know if I am talking to ghosts or not in this forum, but maybe one day .. somebody besides me will find this helpful.
There are two bugs in the DropDownBox widget
1. It is expanded (i.e. showing list) when dialog is created.
Solution: Overide setShow Base function:
Add this function to the class:
def setShow(self, value):
2. Selection handler is not called
Solution: Add this line in _pyuiMouseDown after "if not set.hit(event.pos)"