Installing Rails 2.0

Help! I cant install Rails 2.0. Can anybody help me?

kb1@kb1-laptop:~/zeugs/rails/blog$ ruby script/server
Missing the Rails 2.0 gem. Please `gem install -v=2.0 rails`, update
your RAILS_GEM_VERSION setting in config/environment.rb for the Rails
version you do have installed, or comment out RAILS_GEM_VERSION to use
the latest version installed.
kb1@kb1-laptop:~/zeugs/rails/blog$ sudo gem install -v=2.0 rails
[sudo] password for kb1:
ERROR: Error installing rails:
        rails requires activeresource (= 2.0.0, runtime)

But now what?
I uninstall rails 2.1 and actionmailer, actionpack etc. in version 2.1 -
but this dont solve my problem.

kb1@kb1-laptop:~/zeugs/rails/blog$ sudo gem list

*** LOCAL GEMS ***

actionmailer (2.0.0)
actionpack (2.0.0)
activerecord (2.0.0)
activesupport (2.0.0)
cgi_multipart_eof_fix (2.5.0)
daemons (1.0.10)
fastthread (1.0.1)
gem_plugin (0.2.3)
mongrel (1.1.5)
mysql (2.7)
rake (0.8.1)
sqlite3-ruby (1.2.2)
kb1@kb1-laptop:~/zeugs/rails/blog$ sudo gem install -v=2.0 rails
ERROR: Error installing rails:
        rails requires activeresource (= 2.0.0, runtime)

what can i do?
Using Ubuntu 32Bit. Using Ruby from synaptics and installed rubygems by
hand through the tar.gz package.

solved it by installing rails 2.0.2!