ruby and rails wont work even they're already installed

mongskie@mongskie-os:~$ gem /usr/bin/gem:4: undefined method `manage_gems' for Gem:Module (NoMethodError)

mongskie@mongskie-os:~$ rails /usr/lib/ruby/1.8/active_support/dependencies.rb:55: uninitialized constant ActiveSupport::Dependencies::Mutex (NameError)   from /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:36:in `gem_original_require'   from /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:36:in `require'   from /usr/lib/ruby/1.8/active_support.rb:56   from /usr/share/rails-ruby1.8/railties/bin/../lib/rails_generator.rb: 28:in `require'   from /usr/share/rails-ruby1.8/railties/bin/../lib/rails_generator.rb: 28   from /usr/share/rails-ruby1.8/railties/bin/rails:14:in `require'   from /usr/share/rails-ruby1.8/railties/bin/rails:14

I always get these messages. Why is this. Pls help me.

I can only advise you to use rvm (type this in Google ) and update your Ruby and rails to newest version.

If you can’t update Rails or downgrade RubyGems, you need to require ‘thread’ before boot.rb runs, in three files: Rakefile, script/server, and config/environment.rb. It seems older versions of Rails relied on a require from RubyGems, giving us that delightful error message upon updating RubyGems to a newer version, which does not require thread.rb by default. More info: