RubyGemsを入れようとしてトラブった on Windows

ruby-1.8.7-p72-i386-mswin32.zip に rubygems-1.3.0.zip を入れようとしたら「undefined method `uid' for nil:NilClass (NoMethodError)」なるエラーが出て、セットアップできない。

C:\ruby\bin>ruby setup.rb

(...省略...)

Installing rubygems-1.3.0 ri into d:/ruby-1.8.7-p72-i386-mswin32/lib/ruby/gems/1.8/doc/rubygems-1.3.0/ri
./lib/rubygems.rb:713:in `set_paths': undefined method `uid' for nil:NilClass (NoMethodError)
        from ./lib/rubygems.rb:711:in `each'
        from ./lib/rubygems.rb:711:in `set_paths'
        from ./lib/rubygems.rb:518:in `path'
        from ./lib/rubygems/source_index.rb:66:in `installed_spec_directories'
        from ./lib/rubygems/source_index.rb:56:in `from_installed_gems'
        from ./lib/rubygems.rb:726:in `source_index'
        from ./lib/rubygems.rb:138:in `activate'
        from ./lib/rubygems.rb:49:in `gem'
        from setup.rb:279:in `run_rdoc'
        from setup.rb:296

原因はさておき、rubygems-1.2.0.zip なら問題なくセットアップできた。