error installing rails on ubuntu linux

I got the following while attempting to install rails on Ubuntu 6.06
LTS with Ruby 1.8.4:

tim@tim-ubuntu:~/Desktop/rubygems-0.9.0$ sudo gem install rails
--include-dependencies
Bulk updating Gem source index for: http://gems.rubyforge.org
Successfully installed rails-1.1.6
Successfully installed rake-0.7.1
Successfully installed activesupport-1.3.1
Successfully installed activerecord-1.14.4
Successfully installed actionpack-1.12.5
Successfully installed actionmailer-1.2.5
Successfully installed actionwebservice-1.1.6
/usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:27:in
`gem_original_require': no such file to load -- rdoc/rdoc (LoadError)
        from
/usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:27:in `require'
        from /usr/local/lib/site_ruby/1.8/rubygems/doc_manager.rb:71:in
`load_rdoc'
        from /usr/local/lib/site_ruby/1.8/rubygems/doc_manager.rb:41:in
`generate_ri'
        from
/usr/local/lib/site_ruby/1.8/rubygems/gem_commands.rb:283:in `execute'
        from
/usr/local/lib/site_ruby/1.8/rubygems/gem_commands.rb:282:in `execute'
        from
/usr/local/lib/site_ruby/1.8/rubygems/gem_commands.rb:220:in `execute'
        from /usr/local/lib/site_ruby/1.8/rubygems/command.rb:69:in
`invoke'
        from
/usr/local/lib/site_ruby/1.8/rubygems/cmd_manager.rb:117:in
`process_args'
        from /usr/local/lib/site_ruby/1.8/rubygems/cmd_manager.rb:88:in
`run'
        from /usr/local/lib/site_ruby/1.8/rubygems/gem_runner.rb:29:in
`run'
        from /usr/bin/gem:23

Has anyone experienced this? Any ideas exactly whats going on or how
to correct it?

Thanks!
Tim

Is rdoc installed? You should use synaptic/apt-get to install ruby,
rdoc, ri and irb. Gems should be installed from source (following
instructions at www.rubyonrails.com/down), but it looks like you've got
gems installed already. Then re-run 'sudo gem install rails
--include-dependencies' and that should work much better. No need to
start from scratch. You're almost there. It's just that the
Debian/Ubuntu people seem to like breaking packages into many tiny
pieces, so just because you have 'ruby' installed doesn't mean you have
all the other pieces to have a fully working ruby for
installing/running rails.