FWIW I too see that error (I am in Tokyo, too).

Assuming you are using Bundler, and not trying to install the jekyll gem globally, you can manually specify a server in the Gemfile.

In an empty directory, I created a Gemfile with only these contents:

    source 'http://production.s3.rubygems.org'
    
    gem 'jekyll', '~> 2.0'

Then on the command line:

    [mason@IT-PC-MACPRO-002 jekyll-2-fuckery]$ bundle install --path vendor/bundle
    Fetching source index from http://production.s3.rubygems.org/
    Resolving dependencies.................
    Using blankslate 2.1.2.4
    <bunch of lines deleted...>
    Your bundle is complete!
    It was installed into ./vendor/bundle
    [mason@IT-PC-MACPRO-002 jekyll-2-fuckery]$ bundle exec jekyll --version
    jekyll 2.0.2
    [mason@IT-PC-MACPRO-002 jekyll-2-fuckery]$ 

That worked.

(EDIT: Updated with server that worked.)