Problem saving parent and children using belongs_to, class_name, and foreign_key

Hi, I have a real simple association setup here that's just trying to:
- Create a new PayjunctionOrder
- Create some LineItem objects and assign them to the PayjunctionOrder
- Save everything

I'm using Rails Edge.

Here are the table schemas for reference:

  create_table "line_items", :force => true do |t|
    t.column "product_id", :integer,
:default => 0, :null => false
    t.column "order_id", :integer,
:default => 0, :null => false
    t.column "quantity", :integer,
:default => 0, :null => false
    t.column "total_price", :decimal, :precision => 8, :scale => 2,
:default => 0.0, :null => false
  end

  create_table "payjunction_orders", :force => true do |t|
    t.column "total_amount", :decimal, :precision => 8, :scale =>
2, :default => 0.0, :null => false
    t.column "response_code", :string, :limit => 5, :default => "",
:null => false
    t.column "response_message", :string
    t.column "tracking_code", :string, :limit => 15
    t.column "cc_last_four", :string, :limit => 22
    t.column "first_name", :string, :limit => 30
    t.column "last_name", :string, :limit => 20
    t.column "email", :string, :limit => 30
  end

I finally got this sorted, so here's the solution for anyone else with
this problem.

Seems that the parent class also needs to know what the foreign key is
called in the child. So, you'd need the following: