Ruby on Rails

Hi guys,
I'm having a problem that's driving me nuts.
I have a rails 3.1.1 project in which bundler is ignoring RSpec, no
matter what I set rspec or rspec-rails it never gets installed.
I've tried bundler 1.0.21 and bundler pre.
Any clue would be very much appreciated.

Thaks a lot in advance.

This is my Gemfile

source 'http://rubygems.org'

gem 'rails', '3.1.1'

# Gems used only for assets and not required
# in production environments by default.
group :assets do
gem 'sass-rails', "~> 3.1.0.rc"
gem 'coffee-rails', "~> 3.1.0.rc"
gem 'uglifier'
end

gem 'json'
gem 'jquery-rails'
gem 'haml-rails'
gem 'compass', '>= 0.11.5'
gem 'omniauth', '>=0.3.0'
gem 'kaminari'
gem 'bcrypt-ruby'
gem 'exception_notification'
gem 'execjs'
gem 'therubyracer'
#group :development do
##gem 'ruby-debug19'