Depois de criar um novo aplicativo de rails Após o blog oficial de railsposta, a tentativa de converter aplicativos para os trilhos 3.2.0.rc2 produz o seguinte

Updated Gemfile to depend on rails ~> 3.2.0.rc2
    gem 'rails', '~>3.2.0.rc2'
Updated Gemfile to depend on sass-rails ~> 3.2.3
    gem 'sass-rails',   '~> 3.2.3'

$ bundle install
Fetching source index for http://rubygems.org/
Bundler could not find compatible versions for gem "activesupport":
  In snapshot (Gemfile.lock):
    activesupport (3.1.1)

  In Gemfile:
    rails (~> 3.2.0.rc2) ruby depends on
      activesupport (= 3.2.0.rc2) ruby

Running `bundle update` will rebuild your snapshot from scratch, using 
only the gems in your Gemfile, which may resolve the conflict.

$bundle update
Fetching source index for http://rubygems.org/
Bundler could not find compatible versions for gem "railties":
  In Gemfile:
    coffee-rails (~> 3.1.1) ruby depends on
      railties (~> 3.1.0) ruby

    rails (~> 3.2.0.rc2) ruby depends on
      railties (3.2.0.rc2)

Qual é exatamente o problema?

Especificações do sistema:

Mac OS 10.7.2, Xcode 4.2.1, rvm 1.10.1 usando ruby 1.9.3p0 (revisão de 2011-10-30 33570) [x86_64-darwin11.2.0]