Rspec freezes periodically when using capybara-webkit with a page loading an external script with async = true

I am working on an application using uservoice. Uservoice snippet

  var uv = document.createElement('script');
  uv.type = 'text/javascript';
  uv.async = true;
  uv.src = ...; // external call to uservoice to fetch js
  var s = document.getElementsByTagName('script')[0];
  ...

This javascript is loaded on all pages. At startup, the rake speclaunch will hang periodically. All tests run smoothly when I delete the uservoice fragment. I tried the installation Capybara.javascript_driver = :webkit_debugand I do not see the answer from uservoice. When I install page.driver.browser.timeout, I see a 0 response from uservoice, and the specifications will fail with a timeout error.

Anyone else run into this problem?