Rake version 0.9 is currently breaking Rails. Error is occurring every time a rake task is invoked:

rake aborted!
undefined method `task

I am sure that patch is on its way. Until that you can use Rake 0.8.7 or monkey patch Rakefile like is’t originally suggested here

module ::NameOfYoursRailsApp
  class Application
    include Rake::DSL
  end
end

module ::RakeFileUtils
  extend Rake::FileUtilsExt
end

–