TypeError: Mail is not a module

I have been stepping through the introduction of the Action Mailer
Basics page at: http://edgeguides.rubyonrails.org/action_mailer_basics.html

I went through the steps through 2.1.3 Create a Mailer View (with
some variation of content)
I skipped 2.1.4, generating a user, since I already had a user class.

But I copied the line of code:

     UserMailer.welcome_email(@user).deliver

into my user controller in the context of an action, changing it to:

UserMailer.welcome_new_contact( tom, hagrid)

where the 'tom' and 'hagrid' are both users.

And I get this horrible error message:

     TypeError (Mail is not a module):
       app/mailers/user_mailer.rb:1:in `<top (required)>'
       app/controllers/users_controller.rb:285:in `mail_contact'
       app/controllers/users_controller.rb:409:in `add_contact'

Running if from the console gives me this error:

TypeError: Mail is not a module
  from /opt/cmf/cloudfiles/ruby/1.9.1/gems/actionmailer-3.1.0.rc6/lib/
action_mailer/tmail_compat.rb:1:in `<top (required)>'
  from /opt/cmf/cloudfiles/ruby/1.9.1/gems/activesupport-3.1.0.rc6/lib/
active_support/dependencies.rb:237:in `require'
  from /opt/cmf/cloudfiles/ruby/1.9.1/gems/activesupport-3.1.0.rc6/lib/
active_support/dependencies.rb:237:in `block in require'
  from /opt/cmf/cloudfiles/ruby/1.9.1/gems/activesupport-3.1.0.rc6/lib/
active_support/dependencies.rb:223:in `block in load_dependency'
  from /opt/cmf/cloudfiles/ruby/1.9.1/gems/activesupport-3.1.0.rc6/lib/
active_support/dependencies.rb:636:in `new_constants_in'
  from /opt/cmf/cloudfiles/ruby/1.9.1/gems/activesupport-3.1.0.rc6/lib/
active_support/dependencies.rb:223:in `load_dependency'
  from /opt/cmf/cloudfiles/ruby/1.9.1/gems/activesupport-3.1.0.rc6/lib/
active_support/dependencies.rb:237:in `require'
  from /opt/cmf/cloudfiles/ruby/1.9.1/gems/actionmailer-3.1.0.rc6/lib/
action_mailer/base.rb:2:in `<top (required)>'
  from /opt/cmf/app/mailers/user_mailer.rb:3:in `<top (required)>'
  from /opt/cmf/cloudfiles/ruby/1.9.1/gems/activesupport-3.1.0.rc6/lib/
active_support/dependencies.rb:452:in `load'
  from /opt/cmf/cloudfiles/ruby/1.9.1/gems/activesupport-3.1.0.rc6/lib/
active_support/dependencies.rb:452:in `block in load_file'
  from /opt/cmf/cloudfiles/ruby/1.9.1/gems/activesupport-3.1.0.rc6/lib/
active_support/dependencies.rb:636:in `new_constants_in'
  from /opt/cmf/cloudfiles/ruby/1.9.1/gems/activesupport-3.1.0.rc6/lib/
active_support/dependencies.rb:451:in `load_file'
  from /opt/cmf/cloudfiles/ruby/1.9.1/gems/activesupport-3.1.0.rc6/lib/
active_support/dependencies.rb:338:in `require_or_load'
  from /opt/cmf/cloudfiles/ruby/1.9.1/gems/activesupport-3.1.0.rc6/lib/
active_support/dependencies.rb:485:in `load_missing_constant'
  from /opt/cmf/cloudfiles/ruby/1.9.1/gems/activesupport-3.1.0.rc6/lib/
active_support/dependencies.rb:181:in `block in const_missing'
  from /opt/cmf/cloudfiles/ruby/1.9.1/gems/activesupport-3.1.0.rc6/lib/
active_support/dependencies.rb:179:in `each'
  from /opt/cmf/cloudfiles/ruby/1.9.1/gems/activesupport-3.1.0.rc6/lib/
active_support/dependencies.rb:179:in `const_missing'
  from (irb):4
  from /opt/cmf/cloudfiles/ruby/1.9.1/gems/railties-3.1.0.rc6/lib/rails/
commands/console.rb:45:in `start'
  from /opt/cmf/cloudfiles/ruby/1.9.1/gems/railties-3.1.0.rc6/lib/rails/
commands/console.rb:8:in `start'
  from /opt/cmf/cloudfiles/ruby/1.9.1/gems/railties-3.1.0.rc6/lib/rails/
commands.rb:40:in `<top (required)>'
  from script/rails:6:in `require'

Can anyone clue me in as to what is going on?