Weird error after upgrading to rails 3.0.4

Hey folks,

have you seen this ever?

[user@i ~/rails_project]$ rake rails:update --trace
(in /usr/home/rails_project)
rake aborted!
uninitialized constant ActiveModel::Validations::HelperMethods
/usr/local/lib/ruby/gems/1.8/gems/activemodel-3.0.4/lib/active_model/
validations.rb:50
/usr/local/lib/ruby/gems/1.8/gems/activesupport-3.0.4/lib/
active_support/concern.rb:52:in `class_eval'
/usr/local/lib/ruby/gems/1.8/gems/activesupport-3.0.4/lib/
active_support/concern.rb:52:in `append_features'
/usr/local/lib/ruby/gems/1.8/gems/activesupport-3.0.4/lib/
active_support/concern.rb:48:in `include'
/usr/local/lib/ruby/gems/1.8/gems/activesupport-3.0.4/lib/
active_support/concern.rb:48:in `send'
/usr/local/lib/ruby/gems/1.8/gems/activesupport-3.0.4/lib/
active_support/concern.rb:48:in `append_features'
/usr/local/lib/ruby/gems/1.8/gems/activesupport-3.0.4/lib/
active_support/concern.rb:48:in `each'
/usr/local/lib/ruby/gems/1.8/gems/activesupport-3.0.4/lib/
active_support/concern.rb:48:in `append_features'
...

Regards,
Istvan