Can't dup NilClass problem

Using RubyGems 1.6.2, this doesn't work:

$ gem install be9-acl9 --source http://gems.github.com --debug

Yielding this results:

Exception `NameError' at /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/command_manager.rb:163 - uninitialized constant Gem::Commands::InstallCommand
Exception `LoadError' at /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36 - no such file to load -- psych
Exception `LoadError' at /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:61 - no such file to load -- psych
Exception `Errno::EEXIST' at /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/1.8/fileutils.rb:243 - File exists - /Users/fcoury/.gem/specs/gems.github.com%80
Exception `IOError' at /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/format.rb:45 - closed stream
Exception `Errno::EEXIST' at /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/1.8/fileutils.rb:243 - File exists - /Users/fcoury/.rvm/gems/ree-1.8.7-2011.03
Exception `Errno::EEXIST' at /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/1.8/fileutils.rb:243 - File exists - /Users/fcoury/.rvm/gems/ree-1.8.7-2011.03/gems/be9-acl9-0.11.0
Exception `TypeError' at /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/specification.rb:442 - can't dup NilClass
ERROR:  While executing gem ... (TypeError)
    can't dup NilClass
    /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/specification.rb:442:in `dup'
    /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/specification.rb:442:in `initialize_copy'
    /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/specification.rb:439:in `each'
    /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/specification.rb:439:in `initialize_copy'
    /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/specification.rb:832:in `dup'
    /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/specification.rb:832:in `to_ruby_for_cache'
    /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/installer.rb:234:in `write_spec'
    /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/installer.rb:175:in `install'
    /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/dependency_installer.rb:299:in `install'
    /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/dependency_installer.rb:270:in `each'
    /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/dependency_installer.rb:270:in `install'
    /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/commands/install_command.rb:120:in `execute'
    /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/commands/install_command.rb:115:in `each'
    /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/commands/install_command.rb:115:in `execute'
    /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/command.rb:278:in `invoke'
    /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/command_manager.rb:133:in `process_args'
    /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/command_manager.rb:103:in `run'
    /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/gem_runner.rb:63:in `run'
    /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/bin/gem:21

While with 1.4.2:

    $ gem install be9-acl9 --source http://gems.github.com --debug
    Exception `NameError' at /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/command_manager.rb:164 - uninitialized constant Gem::Commands::InstallCommand
    Exception `Gem::LoadError' at /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems.rb:812 - Could not find RubyGem test-unit (>= 0)

    Exception `Errno::EEXIST' at /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/1.8/fileutils.rb:243 - File exists - /Users/fcoury/.gem/specs/gems.rubyforge.org%80
    Exception `Errno::EEXIST' at /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/1.8/fileutils.rb:243 - File exists - /Users/fcoury/.gem/specs/gems.github.com%80
    Exception `IOError' at /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/format.rb:46 - closed stream
    Exception `Errno::EEXIST' at /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/1.8/fileutils.rb:243 - File exists - /Users/fcoury/.rvm/gems/ree-1.8.7-2011.03
    Exception `Errno::EEXIST' at /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/1.8/fileutils.rb:243 - File exists - /Users/fcoury/.rvm/gems/ree-1.8.7-2011.03/gems/be9-acl9-0.11.0
    Exception `Errno::EEXIST' at /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/1.8/fileutils.rb:243 - File exists - /Users/fcoury/.rvm/gems/ree-1.8.7-2011.03/gems/be9-acl9-0.11.0
    Exception `Errno::EEXIST' at /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/1.8/fileutils.rb:243 - File exists - /Users/fcoury/.rvm/gems/ree-1.8.7-2011.03/gems/be9-acl9-0.11.0/lib
    Exception `Errno::EEXIST' at /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/1.8/fileutils.rb:243 - File exists - /Users/fcoury/.rvm/gems/ree-1.8.7-2011.03/gems/be9-acl9-0.11.0/lib/acl9
    Exception `Errno::EEXIST' at /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/1.8/fileutils.rb:243 - File exists - /Users/fcoury/.rvm/gems/ree-1.8.7-2011.03/gems/be9-acl9-0.11.0/lib/acl9/controller_extensions
    Exception `Errno::EEXIST' at /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/1.8/fileutils.rb:243 - File exists - /Users/fcoury/.rvm/gems/ree-1.8.7-2011.03/gems/be9-acl9-0.11.0/lib/acl9/model_extensions
    Exception `Errno::EEXIST' at /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/1.8/fileutils.rb:243 - File exists - /Users/fcoury/.rvm/gems/ree-1.8.7-2011.03/gems/be9-acl9-0.11.0/test
    Exception `Errno::EEXIST' at /Users/fcoury/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/1.8/fileutils.rb:243 - File exists - /Users/fcoury/.rvm/gems/ree-1.8.7-2011.03/gems/be9-acl9-0.11.0/test/support
    Successfully installed be9-acl9-0.11.0
    1 gem installed