转载：http://hi.baidu.com/linuxerror/blog/item/f687603be6f5212871cf6cc3.html
: uninitialized constant ActiveSupport::Dependencies::Mutex(NameError)
from/usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:36:in`gem_original_require'
from /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:36:in `require'
from /usr/lib/ruby/gems/1.8/gems/activesupport-2.3.8/lib/active_support.rb:57
from /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:36:in `gem_original_require'
from/usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:36:in`require'
from /usr/lib/ruby/gems/1.8/gems/rails-2.3.8/lib/rails_generator.rb:31
from /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:36:in `gem_original_require'
from /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:36:in `require'
from/usr/lib/ruby/gems/1.8/gems/rails-2.3.8/bin/rails:15
from/usr/bin/rails:19:in`load'
from /usr/bin/rails:19
============================
from:http://stackoverflow.com/questions/5176782/uninitialized-constant-activesupportdependenciesmutex-nameerror
解决方案：
This is an incompatibility between Rails 2.3.8 and recent versions of RubyGems. Upgrade to the latest 2.3 version (2.3.11 as of today).
1.升级rails
2.gem降级 ---> gem update --system 1.5.3
3.require 'thread'
原文推荐：推荐降级的方式，rails的版本兼容有些问题。
个人推荐：require 'thread'