Perhaps the silent upgrade of selenium-webdriver freaked out CI. Let's see.

Gemfile

@@ -73,6 +73,7 @@ end
 group :test do
   gem 'factory_girl_rails'
   gem 'fixture_builder', '~> 0.2.0'
+  gem 'selenium-webdriver', '0.1.3'
   gem 'capybara', '~> 0.3.9'
   gem 'cucumber-rails', '0.3.2'
   gem 'rspec', '>= 2.0.0'

Gemfile.lock

@@ -436,6 +436,7 @@ DEPENDENCIES
   rspec-instafail (>= 0.1.7)
   rspec-rails (>= 2.0.0)
   ruby-debug
+  selenium-webdriver (= 0.1.3)
   thin (= 1.2.8)
   twitter!
   typhoeus