I have this error message and don't know what to do

class AddPrice < ActiveRecord::Migration
  def self.up
  add_column :products, :price, :decimal, :precision => 8, :scale => 2,
:default => 0
  end

  def self.down
  remove_column :products, :price
  end
end

This looks fine - and works on my machine.
Try running with trace:

rake db:migrate --trace

I don't think rails 1.1.6 supports decimal types but 1.2.1 is supposed
to

You probably need to upgrade rails and your app

Craig