Ryan Davis just posted about a problem he helped to diagnose that relates back to an earlier version of Spec::Ui (which ships with RSpec).

The first version of Spec:Ui was called web_spec, and it (unfortunately and erroneously) got installed as a gem when you installed RSpec 0.7.5.

If you have this in your gems directory, kindly send it on its merry way. It’s broken, and will break your stuff (read Ryan’s blog post for details).