First I'd like to note that GetSelectedIndex and SetSelectedIndex are not documented and need to be. They are an integral part of any list box.
GetSelectedIndex works fine, but SetSelectedIndex has no effect. Not only should SetSelectedIndex actually set the selection, if you pass 0 or nil it should clear the selection.
In my case I'm moving items from one list box to another and need to programatically (from lua) exert some control over what is selected in the list boxes.
If I'm just missing something, please explain.