problem with devise

rails g scaffold project name:string email:string

Started GET "/users/sign_in" for 127.0.0.1 at 2012-06-06 21:41:18 +0800
Processing by Devise::SessionsController#new as HTML
  Rendered devise/sessions/new.html.erb within layouts/application (48.2ms)
Completed 500 Internal Server Error in 192ms

ActionView::Template::Error (wrong number of arguments (3 for 2)):
    1: <h2>Sign in</h2>
    2: 
    3: <%= form_for(resource_name, resource, :url => session_path(resource_name)) do |f| %>
    4:   <p><%= f.label :email %></p>
    5:   <p><%= f.text_field :email %></p>
    6: 
  app/views/devise/sessions/new.html.erb:3:in `_app_views_devise_sessions_new_html_erb___134984050_86236200'


  Rendered /home/jay/.rvm/gems/ruby-1.9.3-p125/gems/actionpack-3.2.3/lib/action_dispatch/middleware/templates/rescues/_trace.erb (8.3ms)
  Rendered /home/jay/.rvm/gems/ruby-1.9.3-p125/gems/actionpack-3.2.3/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb (1.4ms)
  Rendered /home/jay/.rvm/gems/ruby-1.9.3-p125/gems/actionpack-3.2.3/lib/action_dispatch/middleware/templates/rescues/template_error.erb within rescues/layout (60.7ms)