Spree admin panel not working - ruby-on-rails

Question

I've install Spree gem and run it as it wrote in Getting Started. All works fine but if I want to go in the Products section in admin panel I have the following error:
Mysql2::Error: Unknown column 'variants.position' in 'order clause': SELECT `variants`.* FROM `variants` WHERE (`variants`.product_id IN (706676762,569012001,723959550,1025786064,1060500592,248786582,187438981,1035865702,459084718) AND (variants.is_master = 0 AND variants.deleted_at IS NULL)) ORDER BY variants.position ASC
Anyone faced that?
EDIT: Here is my Gemfile
source 'http://rubygems.org'
gem 'rails', '3.0.7'
# Bundle edge Rails instead:
# gem 'rails', :git => 'git://github.com/rails/rails.git'
gem 'mysql2', '~> 0.2.11'
gem 'heroku'
gem 'thin'
gem 'spree', '~> 0.60.0'
# Use unicorn as the web server
# gem 'unicorn'
# Deploy with Capistrano
# gem 'capistrano'
# To use debugger (ruby-debug for Ruby 1.8.7+, ruby-debug19 for Ruby 1.9.2+)
# gem 'ruby-debug'
# gem 'ruby-debug19', :require => 'ruby-debug'
# Bundle the extra gems:
# gem 'bj'
# gem 'nokogiri'
# gem 'sqlite3-ruby', :require => 'sqlite3'
# gem 'aws-s3', :require => 'aws/s3'
# Bundle gems for the local environment. Make sure to
# put test-only gems in this group so their generators
# and rake tasks are available in development mode:
# group :development, :test do
# gem 'webrat'
# end
gem "test", :path => "test", :require => "test"

Answer 1

Normally when you install spree by following these steps, you should have some migration files inside db/migrate, one of them contain the missing column for your application :
class AddPositionToVariants < ActiveRecord::Migration
def self.up
add_column :variants, :position, :integer
end
def self.down
remove_column :variants, :position
end
end