rails sで、いつも通り立ち上がらないです。

rails sすると・・・

学習していたのはドットインストールの『Ruby on Rails 4入門』の、レッスン20『Tasksの設定をしていこう』です。→http://dotinstall.com/lessons/basic_rails_v2/24920

順調に進んでいたのですが、途中で異変が。

rails sするとこんな感じで立ち上がらない。

=> Booting WEBrick
=> Rails 4.1.0 application starting in development on http://0.0.0.0:3000
=> Run rails server -h for more startup options
=> Notice: server is listening on all interfaces (0.0.0.0). Consider using 127.0.0.1 (--binding option)
=> Ctrl-C to shutdown server
Exiting
/Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/actionpack-4.1.0/lib/action_dispatch/routing/route_set.rb:327:in eval_block': undefined method arity' for nil:NilClass (NoMethodError)
from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/actionpack-4.1.0/lib/action_dispatch/routing/route_set.rb:313:in draw' from /Users/shimizutakuya/taskapp/config/routes.rb:1:in '
from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/activesupport-4.1.0/lib/active_support/dependencies.rb:241:in load' from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/activesupport-4.1.0/lib/active_support/dependencies.rb:241:in block in load'
from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/activesupport-4.1.0/lib/active_support/dependencies.rb:232:in load_dependency' from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/activesupport-4.1.0/lib/active_support/dependencies.rb:241:in load'
from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.0/lib/rails/application/routes_reloader.rb:40:in block in load_paths' from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.0/lib/rails/application/routes_reloader.rb:40:in each'
from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.0/lib/rails/application/routes_reloader.rb:40:in load_paths' from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.0/lib/rails/application/routes_reloader.rb:16:in reload!'
from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.0/lib/rails/application/routes_reloader.rb:26:in block in updater' from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/activesupport-4.1.0/lib/active_support/file_update_checker.rb:75:in call'
from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/activesupport-4.1.0/lib/active_support/file_update_checker.rb:75:in execute' from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.0/lib/rails/application/routes_reloader.rb:27:in updater'
from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.0/lib/rails/application/routes_reloader.rb:7:in execute_if_updated' from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.0/lib/rails/application/finisher.rb:71:in block in module:Finisher'
from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.0/lib/rails/initializable.rb:30:in instance_exec' from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.0/lib/rails/initializable.rb:30:in run'
from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.0/lib/rails/initializable.rb:55:in block in run_initializers' from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/2.1.0/tsort.rb:226:in block in tsort_each'
from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/2.1.0/tsort.rb:348:in block (2 levels) in each_strongly_connected_component' from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/2.1.0/tsort.rb:427:in each_strongly_connected_component_from'
from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/2.1.0/tsort.rb:347:in block in each_strongly_connected_component' from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/2.1.0/tsort.rb:345:in each'
from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/2.1.0/tsort.rb:345:in call' from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/2.1.0/tsort.rb:345:in each_strongly_connected_component'
from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/2.1.0/tsort.rb:224:in tsort_each' from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/2.1.0/tsort.rb:205:in tsort_each'
from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.0/lib/rails/initializable.rb:54:in run_initializers' from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.0/lib/rails/application.rb:288:in initialize!'
from /Users/shimizutakuya/taskapp/config/environment.rb:5:in <top (required)>' from /Users/shimizutakuya/taskapp/config.ru:3:in require'
from /Users/shimizutakuya/taskapp/config.ru:3:in block in <main>' from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/rack-1.5.2/lib/rack/builder.rb:55:in instance_eval'
from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/rack-1.5.2/lib/rack/builder.rb:55:in initialize' from /Users/shimizutakuya/taskapp/config.ru:in new'
from /Users/shimizutakuya/taskapp/config.ru:in <main>' from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/rack-1.5.2/lib/rack/builder.rb:49:in eval'
from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/rack-1.5.2/lib/rack/builder.rb:49:in new_from_string' from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/rack-1.5.2/lib/rack/builder.rb:40:in parse_file'
from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/rack-1.5.2/lib/rack/server.rb:277:in build_app_and_options_from_config' from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/rack-1.5.2/lib/rack/server.rb:199:in app'
from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.0/lib/rails/commands/server.rb:50:in app' from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/rack-1.5.2/lib/rack/server.rb:314:in wrapped_app'
from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.0/lib/rails/commands/server.rb:130:in log_to_stdout' from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.0/lib/rails/commands/server.rb:67:in start'
from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.0/lib/rails/commands/commands_tasks.rb:81:in block in server' from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.0/lib/rails/commands/commands_tasks.rb:76:in tap'
from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.0/lib/rails/commands/commands_tasks.rb:76:in server' from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.0/lib/rails/commands/commands_tasks.rb:40:in run_command!'
from /Users/shimizutakuya/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.0/lib/rails/commands.rb:17:in <top (required)>' from bin/rails:4:in require'
from bin/rails:4:in `'

参考になりそうなサイトは・・・

binの場所が変わったことが原因？
http://u16suzu.hatenablog.com/entry/20130414/1365935728

しかし、これも試すもrails sで立ち上がらず。

pidファイルを消す？
http://qiita.com/pakiran/items/53c42257ab3f95907ab8

しかし、これでもうまくいかず。

どなたかお知恵をお貸しくださいませ・・・。