The new recommended Ruby version (Ruby 1.9.3p194 with the new RubyGems 1.8.23) introduces a security patch that now verifies SSL certificates. The rubygems.org server is wrongly configured for SSL connections. When someone tries to build a new Rails application, they will get an SSL_connect failure. There's a workaround available. A fix for the server should be forthcoming when the RailsConf ends; the RubyGems team is currently at the conference.