constant ActiveSupport::Dependencies::Mutex (NameError)

Problem:
.rvm/gems/ruby-1.8.7-p299@global/gems/activesupport-2.3.8/lib/active_support/dependencies.rb:55: uninitialized constant ActiveSupport::Dependencies::Mutex (NameError)

Ruby gems version 1.8.14

Resolution:

Downgrade gems. gem update --system 1.5.3