'gem install rails --pre' command break while installing 'Rails 3.1 beta 1'

'gem install rails --pre' command break while installing  'Rails 3.1 beta 1'  with Ruby 1.8.7 but installed successfully with Ruby 1.9.2

I am trying to install 'Rails 3.1 beta 1' on Windows 7. I have already installed Ruby two versions -  'ruby 1.8.7 (2010-08-16 patchlevel 302) [i386-mingw32]' and 'ruby 1.9.2p180 (2011-02-18) [i386-mingw32]' and handling them with pik.

When I ran command 'gem install rails --pre' on Ruby 1.8.7, installation break with following errors:
C:\Users\ritesh>ruby -v
ruby 1.8.7 (2010-08-16 patchlevel 302) [i386-mingw32]

C:\Users\ritesh>gem install rails --pre
Successfully installed multi_json-1.0.2
Successfully installed activesupport-3.1.0.beta1
Successfully installed builder-3.0.0
Successfully installed i18n-0.6.0beta1
Successfully installed activemodel-3.1.0.beta1
Successfully installed rack-1.3.0.beta2
Successfully installed rack-cache-1.0.2
Successfully installed rack-test-0.6.0
Successfully installed rack-mount-0.7.4
Successfully installed hike-1.0.0
Successfully installed tilt-1.3
Successfully installed sprockets-2.0.0.beta.5
Successfully installed erubis-2.7.0
Successfully installed actionpack-3.1.0.beta1
Successfully installed arel-2.1.1
Successfully installed activerecord-3.1.0.beta1
Successfully installed activeresource-3.1.0.beta1
Successfully installed mail-2.3.0
Successfully installed actionmailer-3.1.0.beta1
Successfully installed rack-ssl-1.3.2
Successfully installed railties-3.1.0.beta1
Successfully installed rails-3.1.0.beta1
22 gems installed
Installing ri documentation for multi_json-1.0.2...
Building YARD (yri) index for multi_json-1.0.2...
Installing ri documentation for activesupport-3.1.0.beta1...
Building YARD (yri) index for activesupport-3.1.0.beta1...
Installing ri documentation for builder-3.0.0...
ERROR:  While generating documentation for builder-3.0.0
... MESSAGE:   Unhandled special: Special: type=17, text="<!-- HI -->"
... RDOC args: --ri --op C:/Ruby187/lib/ruby/gems/1.8/doc/builder-3.0.0/ri --title Builder -- Easy XML Building --main README.rdoc --line-numbers --quiet lib CHANGES Rakefile README README.rdoc TAGS doc/releases/builder-1.2.4.rdoc
 doc/releases/builder-2.0.0.rdoc doc/releases/builder-2.1.1.rdoc --title builder-3.0.0 Documentation
(continuing with the rest of the installation)
Building YARD (yri) index for builder-3.0.0...
Installing ri documentation for i18n-0.6.0beta1...
Building YARD (yri) index for i18n-0.6.0beta1...
Installing ri documentation for activemodel-3.1.0.beta1...
Building YARD (yri) index for activemodel-3.1.0.beta1...
Installing ri documentation for rack-1.3.0.beta2...
Building YARD (yri) index for rack-1.3.0.beta2...
Installing ri documentation for rack-cache-1.0.2...
Building YARD (yri) index for rack-cache-1.0.2...
Installing ri documentation for rack-test-0.6.0...
Building YARD (yri) index for rack-test-0.6.0...
Installing ri documentation for rack-mount-0.7.4...
Building YARD (yri) index for rack-mount-0.7.4...
Installing ri documentation for hike-1.0.0...
Building YARD (yri) index for hike-1.0.0...
Installing ri documentation for tilt-1.3...
Building YARD (yri) index for tilt-1.3...
Installing ri documentation for sprockets-2.0.0.beta.5...
Building YARD (yri) index for sprockets-2.0.0.beta.5...
Installing ri documentation for erubis-2.7.0...
Building YARD (yri) index for erubis-2.7.0...
Installing ri documentation for actionpack-3.1.0.beta1...
Building YARD (yri) index for actionpack-3.1.0.beta1...
Building YARD (yri) index for arel-2.1.1...
Installing ri documentation for activerecord-3.1.0.beta1...
Building YARD (yri) index for activerecord-3.1.0.beta1...
Installing ri documentation for activeresource-3.1.0.beta1...
Building YARD (yri) index for activeresource-3.1.0.beta1...
Installing ri documentation for mail-2.3.0...
Building YARD (yri) index for mail-2.3.0...
Installing ri documentation for actionmailer-3.1.0.beta1...
Building YARD (yri) index for actionmailer-3.1.0.beta1...
Installing ri documentation for rack-ssl-1.3.2...
Building YARD (yri) index for rack-ssl-1.3.2...
Installing ri documentation for railties-3.1.0.beta1...
Building YARD (yri) index for railties-3.1.0.beta1...
[error]: Unhandled exception in YARD::Handlers::Ruby::Legacy::ModuleHandler:
[error]:   in `lib/rails/generators/rails/plugin_new/templates/lib/%name%/engine.rb`:1:

         1: module <%= camelized %>

[error]: ArgumentError: invalid empty object name
[error]: Stack trace:
        C:/Ruby187/lib/ruby/gems/1.8/gems/yard-0.6.3/lib/yard/code_objects/base.rb:167:in `new'
        C:/Ruby187/lib/ruby/gems/1.8/gems/yard-0.6.3/lib/yard/handlers/ruby/legacy/module_handler.rb:7:in `process'
        C:/Ruby187/lib/ruby/gems/1.8/gems/yard-0.6.3/lib/yard/handlers/processor.rb:90:in `process'
        C:/Ruby187/lib/ruby/gems/1.8/gems/yard-0.6.3/lib/yard/handlers/processor.rb:88:in `each'
        C:/Ruby187/lib/ruby/gems/1.8/gems/yard-0.6.3/lib/yard/handlers/processor.rb:88:in `process'
        C:/Ruby187/lib/ruby/gems/1.8/gems/yard-0.6.3/lib/yard/handlers/ruby/legacy/class_handler.rb:54:in `each_with_index'

Installing ri documentation for rails-3.1.0.beta1...
File not found: lib

Then I switched to Ruby 1.9.2 and tried 'gem install rails --pre' again, and it installed successfully.
C:\Users\ritesh>ruby -v
ruby 1.9.2p180 (2011-02-18) [i386-mingw32]
 
C:\Users\ritesh>gem install rails --pre
Fetching: multi_json-1.0.2.gem (100%)
Fetching: activesupport-3.1.0.beta1.gem (100%)
Fetching: builder-3.0.0.gem (100%)
Fetching: i18n-0.6.0beta1.gem (100%)
Fetching: bcrypt-ruby-2.1.4-x86-mingw32.gem (100%)
Fetching: activemodel-3.1.0.beta1.gem (100%)
Fetching: rack-1.3.0.beta2.gem (100%)
Fetching: rack-cache-1.0.2.gem (100%)
Fetching: rack-test-0.6.0.gem (100%)
Fetching: rack-mount-0.7.4.gem (100%)
Fetching: hike-1.0.0.gem (100%)
Fetching: tilt-1.3.gem (100%)
Fetching: sprockets-2.0.0.beta.5.gem (100%)
Fetching: tzinfo-0.3.27.gem (100%)
Fetching: erubis-2.7.0.gem (100%)
Fetching: actionpack-3.1.0.beta1.gem (100%)
Fetching: arel-2.1.1.gem (100%)
Fetching: activerecord-3.1.0.beta1.gem (100%)
Fetching: activeresource-3.1.0.beta1.gem (100%)
Fetching: mail-2.3.0.gem (100%)
Fetching: actionmailer-3.1.0.beta1.gem (100%)
Fetching: rack-ssl-1.3.2.gem (100%)
Fetching: railties-3.1.0.beta1.gem (100%)
Fetching: rails-3.1.0.beta1.gem (100%)
Successfully installed multi_json-1.0.2
Successfully installed activesupport-3.1.0.beta1
Successfully installed builder-3.0.0
Successfully installed i18n-0.6.0beta1
Successfully installed bcrypt-ruby-2.1.4-x86-mingw32
Successfully installed activemodel-3.1.0.beta1
Successfully installed rack-1.3.0.beta2
Successfully installed rack-cache-1.0.2
Successfully installed rack-test-0.6.0
Successfully installed rack-mount-0.7.4
Successfully installed hike-1.0.0
Successfully installed tilt-1.3
Successfully installed sprockets-2.0.0.beta.5
Successfully installed tzinfo-0.3.27
Successfully installed erubis-2.7.0
Successfully installed actionpack-3.1.0.beta1
Successfully installed arel-2.1.1
Successfully installed activerecord-3.1.0.beta1
Successfully installed activeresource-3.1.0.beta1
Successfully installed mail-2.3.0
Successfully installed actionmailer-3.1.0.beta1
Successfully installed rack-ssl-1.3.2
Successfully installed railties-3.1.0.beta1
Successfully installed rails-3.1.0.beta1
24 gems installed
Installing ri documentation for multi_json-1.0.2...
Installing ri documentation for activesupport-3.1.0.beta1...
Installing ri documentation for builder-3.0.0...
Installing ri documentation for i18n-0.6.0beta1...
Installing ri documentation for bcrypt-ruby-2.1.4-x86-mingw32...
Installing ri documentation for activemodel-3.1.0.beta1...
Installing ri documentation for rack-1.3.0.beta2...
Installing ri documentation for rack-cache-1.0.2...
Installing ri documentation for rack-test-0.6.0...
Installing ri documentation for rack-mount-0.7.4...
Installing ri documentation for hike-1.0.0...
Installing ri documentation for tilt-1.3...
Installing ri documentation for sprockets-2.0.0.beta.5...
Installing ri documentation for tzinfo-0.3.27...
Installing ri documentation for erubis-2.7.0...
Installing ri documentation for actionpack-3.1.0.beta1...
Installing ri documentation for arel-2.1.1...
Installing ri documentation for activerecord-3.1.0.beta1...
Installing ri documentation for activeresource-3.1.0.beta1...
Installing ri documentation for mail-2.3.0...
Installing ri documentation for actionmailer-3.1.0.beta1...
Installing ri documentation for rack-ssl-1.3.2...
Installing ri documentation for railties-3.1.0.beta1...
Installing ri documentation for rails-3.1.0.beta1...
Installing RDoc documentation for multi_json-1.0.2...
Installing RDoc documentation for activesupport-3.1.0.beta1...
ERROR:  While generating documentation for activesupport-3.1.0.beta1
... MESSAGE:   incompatible character encodings: UTF-8 and ASCII-8BIT
... RDOC args: lib
(continuing with the rest of the installation)
Installing RDoc documentation for builder-3.0.0...
Installing RDoc documentation for i18n-0.6.0beta1...
Installing RDoc documentation for bcrypt-ruby-2.1.4-x86-mingw32...
Installing RDoc documentation for activemodel-3.1.0.beta1...
Installing RDoc documentation for rack-1.3.0.beta2...
Installing RDoc documentation for rack-cache-1.0.2...
Installing RDoc documentation for rack-test-0.6.0...
Installing RDoc documentation for rack-mount-0.7.4...
Installing RDoc documentation for hike-1.0.0...
Installing RDoc documentation for tilt-1.3...
Installing RDoc documentation for sprockets-2.0.0.beta.5...
Installing RDoc documentation for tzinfo-0.3.27...
Installing RDoc documentation for erubis-2.7.0...
Installing RDoc documentation for actionpack-3.1.0.beta1...
Installing RDoc documentation for arel-2.1.1...
Installing RDoc documentation for activerecord-3.1.0.beta1...
Installing RDoc documentation for activeresource-3.1.0.beta1...
Installing RDoc documentation for mail-2.3.0...
Installing RDoc documentation for actionmailer-3.1.0.beta1...
Installing RDoc documentation for rack-ssl-1.3.2...
Installing RDoc documentation for railties-3.1.0.beta1...
Installing RDoc documentation for rails-3.1.0.beta1...

C:\Users\ritesh>



I observed some difference when installing with Ruby 1.8.7 and Ruby 1.9.2.

No.1 : When I tried to install 'Rails 3.1 beta 1' with Ruby 1.8.7, installation breaks, but with Ruby 1.9.2 it completes the installation with success.
No.2 : With Ruby 1.8.7 it installed 22 gems and with Ruby 1.9.2 it installed 24 gems
No. 3 :  Its building YARD (yri) index after Installing ri documentation in Ruby 1.8.7, but no such YARD index on Ruby 1.9.2.