Province field not updated on Country change

The province field's AJAX does not successfully update the field's values when the country is changed.

I have the province field widget set to "drop down". When I choose a country, the province drop down still displays:

Please select
NOT LISTED

I have to save the form upon which the form reloads and the options are correct in the State/Province field.

I traced this through to the fact that none of the conditional statements in _location_country_ajax_callback() are actually met, so this function never returns anything. Thus no part of the form is dynamically refreshed.

I'm not really familiar with how fields utilise the fapi AJAX system, but that said, I checked what the field's form builder code is doing... location_locationapi() never receives a form_state() from anywhere... should one of its parents pass this down?

Pretty frustrated that this doesn't work, and willing to dig more, but not sure where to go from here.

See also this related comment elsewhere in the issue queue: http://drupal.org/node/330066#comment-4300950