When you click on an item once it gets the focus, second time
you get an input widget (this is by design, although some means
to automatically get the input widget would be nice). However
when the widget appears it doesn't recieve the mouse event for the
second click, so you must click a 3rd time to activate it (e.g. get
the drop down list from a combo box).
This is a known issue on OS X, but a platform-agnostic work-
around should be implemented.