I\'m attempting to follow railstutorial.org, and am currently on Chapter 7, where you start using factories: http://railstutorial.org/chapters/modeling-and-viewing-users-two#sec
I had this problem, but it was because I had placed the factory girl gem under the development section instead of the test section of the Gemfile. Once under the test section, it worked. One difference I note between my entry and yours is that mine specifies 1.0:
group :test do
gem 'rspec-rails', '2.6.1'
gem 'webrat', '0.7.1'
gem 'factory_girl_rails', '1.0'
end