Criei um script simples no Linux, mas agora estou tentando fazê-lo funcionar no Windows.

O código é:

require 'watir-webdriver'
puts "Press enter when ready to continue"
gets
browser = Watir::Browser.start "http://www.google.com"
# do stuff

Funciona exatamente como o esperado no Ubuntu. Mas quando eu tento no Windows, o processo do Firefox é iniciado, mas depois morre antes que você veja uma janela do Firefox. Esta é uma nova instalação do Ruby nesta instalação do Windows, nunca a usei antes nesta máquina.

Qual poderia ser o problema?

Editar: rastreamento de linha de comando, conforme solicitado.

C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/selenium-webdriver-2.53.1/lib/selenium/webdriver/firefox/launcher.rb:90:in `connect_until_stable': unable to obtain stable firefox connection in 60 seconds (127.0.0.1:7055) (Selenium::WebDriver::Error::WebDriverError)
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/selenium-webdriver-2.53.1/lib/selenium/webdriver/firefox/launcher.rb:55:in `block in launch'
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/selenium-webdriver-2.53.1/lib/selenium/webdriver/common/socket_lock.rb:43:in `locked'
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/selenium-webdriver-2.53.1/lib/selenium/webdriver/firefox/launcher.rb:51:in `launch'
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/selenium-webdriver-2.53.1/lib/selenium/webdriver/firefox/bridge.rb:43:in `initialize'
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/selenium-webdriver-2.53.1/lib/selenium/webdriver/common/driver.rb:53:in `new'
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/selenium-webdriver-2.53.1/lib/selenium/webdriver/common/driver.rb:53:in `for'
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/selenium-webdriver-2.53.1/lib/selenium/webdriver.rb:84:in `for'
    from C:/Ruby22-x64/lib/ruby/gems/2.2.0/gems/watir-webdriver-0.9.1/lib/watir-webdriver/browser.rb:46:in `initialize'
    from bot.rb:8:in `new'
    from bot.rb:8:in `<main>'