OSX に ruby と rails をインストールした後、ラック競合エラーが発生しました。
sudo rails new test -T
/Library/Ruby/Site/1.8/rubygems/specification.rb:1990:in `raise_if_conflicts': Unable to activate actionpack-3.2.13, because rack-1.5.2 conflicts with rack (~> 1.4.5) (Gem::LoadError)
from /Library/Ruby/Site/1.8/rubygems/specification.rb:1163:in `activate'
from /Library/Ruby/Site/1.8/rubygems/specification.rb:1199:in `activate_dependencies'
from /Library/Ruby/Site/1.8/rubygems/specification.rb:1185:in `each'
from /Library/Ruby/Site/1.8/rubygems/specification.rb:1185:in `activate_dependencies'
from /Library/Ruby/Site/1.8/rubygems/specification.rb:1167:in `activate'
from /Library/Ruby/Site/1.8/rubygems/core_ext/kernel_gem.rb:48:in `gem'
from /usr/bin/rails:18