rspec users - Oct 2010 - rspec --help gives undefined method 'Pathname'

Trying to setup environment on xandros linux.
running ruby 1.9
gem 1.3.7

sudo gem install rspec

but when I issue rspec?help
I receive the following
/usr/lib/ruby/gems/1.9/gems/rspec-core-2.0.0/lib/rspec/core/ruby_project.rb:31:in
`ascend_until?: undefined method `Pathname? for
RSpec::Core::RubyProject:Module (NoMethodError) from
/usr/lib/ruby/gems/1.9/gems/rspec-core-2.0.0/lib/rspec/core/ruby_project.rb:27:in
`find_first_parent_containing? from
/usr/lib/ruby/gems/1.9/gems/rspec-core-2.0.0/lib/rspec/core/ruby_project.rb:23:in
`determine_root?

Any help greatly appreciated.
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