InstantRails upgraded from 1.1.6 has problems:.rb:423:in `remove_const': cannot remove Object

I developed a project on RoR 1.1.6 and it works fine.

On my development machine ( Windows XP, InstantRails 1.4) I used gem install rails --source http://gems.rubyonrails.org --include-dependencies and upgraded Rails to 1.1.6.5848

When I tried to start my application, the following error occurs and I couldn't find any clue to solve it. Please help.

C:\RoR1.2\rails_apps\bidhelper_dev>ruby script/server webrick => Booting WEBrick... C:/RoR1.2/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.1.5848/lib/active_suppor t/dependencies.rb:423:in `remove_const': cannot remove Object::ModelTranslation (NameError)         from C:/RoR1.2/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.1.5848/lib/ active_support/dependencies.rb:423:in `send'         from C:/RoR1.2/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.1.5848/lib/ active_support/dependencies.rb:423:in `remove_constant'         from C:/RoR1.2/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.1.5848/lib/ active_support/dependencies.rb:369:in `new_constants_in'         from C:/RoR1.2/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.1.5848/lib/ active_support/dependencies.rb:369:in `each'         from C:/RoR1.2/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.1.5848/lib/ active_support/dependencies.rb:369:in `new_constants_in'         from C:/RoR1.2/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.1.5848/lib/ active_support/dependencies.rb:496:in `require'         from C:/RoR1.2/ruby/lib/ruby/gems/1.8/gems/rails-1.1.6.5848/lib/commands /servers/webrick.rb:52         from C:/RoR1.2/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27 :in `gem_original_require'          ... 7 levels...         from C:/RoR1.2/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.1.5848/lib/ active_support/dependencies.rb:496:in `require'         from C:/RoR1.2/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.1.5848/lib/ active_support/dependencies.rb:343:in `new_constants_in'         from C:/RoR1.2/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.1.5848/lib/ active_support/dependencies.rb:496:in `require'         from script/server:3