Cuando ejecuto una aplicación en Lion OS X, aparece este error:

Unable to load the EventMachine C extension; To use the pure-ruby reactor, require 'em/pure_ruby'
/Users/adam/.rvm/gems/ruby-1.9.2-p290/gems/eventmachine-1.0.0/lib/eventmachine.rb:8:in `require': no such file to load -- rubyeventmachine (LoadError)
    from /Users/adam/.rvm/gems/ruby-1.9.2-p290/gems/eventmachine-1.0.0/lib/eventmachine.rb:8:in `<top (required)>'
    from /Users/adam/.rvm/gems/ruby-1.9.2-p290@global/gems/bundler-1.0.21/lib/bundler/runtime.rb:68:in `require'
    from /Users/adam/.rvm/gems/ruby-1.9.2-p290@global/gems/bundler-1.0.21/lib/bundler/runtime.rb:68:in `block (2 levels) in require'
    from /Users/adam/.rvm/gems/ruby-1.9.2-p290@global/gems/bundler-1.0.21/lib/bundler/runtime.rb:66:in `each'
    from /Users/adam/.rvm/gems/ruby-1.9.2-p290@global/gems/bundler-1.0.21/lib/bundler/runtime.rb:66:in `block in require'
    from /Users/adam/.rvm/gems/ruby-1.9.2-p290@global/gems/bundler-1.0.21/lib/bundler/runtime.rb:55:in `each'
    from /Users/adam/.rvm/gems/ruby-1.9.2-p290@global/gems/bundler-1.0.21/lib/bundler/runtime.rb:55:in `require'
    from /Users/adam/.rvm/gems/ruby-1.9.2-p290@global/gems/bundler-1.0.21/lib/bundler.rb:122:in `require'
    from /Users/adam/rubydev/future_computers/config/application.rb:7:in `<top (required)>'
    from /Users/adam/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.2.1/lib/rails/commands.rb:53:in `require'
    from /Users/adam/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.2.1/lib/rails/commands.rb:53:in `block in <top (required)>'
    from /Users/adam/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.2.1/lib/rails/commands.rb:50:in `tap'
    from /Users/adam/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.2.1/lib/rails/commands.rb:50:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'adam

Realmente no sé cómo solucionar esto, he añadido eleventmachine Gema en el Gemfile, pero no ayudó ...

¿Podría ayudarme, por favor, cómo solucionarlo?

Gracias