If you try to use the authentication solution devise with Rails 3, you have to upgrade the version to 1.1.

First, add the dependency to your local Gemfile:

gem 'devise', "1.1.rc2"

Second, download and install the new version of devise:

gem install devise --version=1.1.rc2

Finally, run the generator:

rails generate devise:install

If the latter does not work, you can try:

bundle install

Additional information can be found at github devise.