Dynamic Select Forms problem - using the Related Select Forms plugin

I've got a webapp that allows people to add locations. I'm trying to
add international support, so I'm restructuring my add location form.

I need for users to select a country, and then have the area auto
populate with results (i.e. pick US, get states, pick Canada, get

I've installed the Related Select Forms plugin from here:

This is where my problems begin

I can get the drop down menus to work fine, if I pick US, i get
states. However, when I add the "form." code to the collection select,
I get this error message:

undefined method `merge' for :name:Symbol

if I take off the form. it loads fine, but when I submit the location,
neither country or state gets saved.

This is the code I'm using:

<% form for :location do |form| %>

<%= form.collection_select(:country, :id,
Country.find(:all), :id, :name, :include_blank => true) %>

<%= submit_tag 'save', :class => "submit" %>

Is this plugin just not able to work with form_for?