Accidentally Updated to Bleeding Edge

Good Afternoon,

I recently bought a new imac and decided to give RoR a try. OS X comes
standard with it, but in “Agile Web Dev with Rails” it suggested I may
want to update. Well, after updating, I can’t get anything to work. I
accidentally ran:

gem update --system

I think this threw my system off. Is there a way to revert rails, ruby
and ruby gems? Any suggestions would be helpful.

Here is one error I am getting:

polygone$ ruby script/generate controller Say
/Library/Ruby/Gems/1.8/gems/activerecord-2.0.2/lib/active_record/base.rb:1532:in
`method_missing': undefined method `partial_updates=' for
ActiveRecord::Base:Class (NoMethodError)
  from
/Users/johnmayer/Documents/testApp/demo/config/initializers/new_rails_defaults.rb:5
  from
/Library/Ruby/Gems/1.8/gems/activesupport-2.0.2/lib/active_support/dependencies.rb:489:in
`load'
  from
/Library/Ruby/Gems/1.8/gems/activesupport-2.0.2/lib/active_support/dependencies.rb:489:in
`load'
  from
/Library/Ruby/Gems/1.8/gems/activesupport-2.0.2/lib/active_support/dependencies.rb:342:in
`new_constants_in'
  from
/Library/Ruby/Gems/1.8/gems/activesupport-2.0.2/lib/active_support/dependencies.rb:489:in
`load'
  from /Library/Ruby/Gems/1.8/gems/rails-2.0.2/lib/initializer.rb:342:in
`load_application_initializers'
  from /Library/Ruby/Gems/1.8/gems/rails-2.0.2/lib/initializer.rb:341:in
`each'
  from /Library/Ruby/Gems/1.8/gems/rails-2.0.2/lib/initializer.rb:341:in
`load_application_initializers'
   ... 6 levels...
  from
/Library/Ruby/Gems/1.8/gems/rails-2.0.2/lib/commands/generate.rb:1
  from /Library/Ruby/Site/1.8/rubygems/custom_require.rb:27:in
`gem_original_require'
  from /Library/Ruby/Site/1.8/rubygems/custom_require.rb:27:in `require'
  from script/generate:3