出现这个情况是为什么？解决思路

出现这个情况是为什么？
C:/Ruby/lib/ruby/gems/1.8/gems/activesupport-2.3.4/lib/active_support/dependenc
es.rb:55: uninitialized constant ActiveSupport::Dependencies::Mutex (NameError)
  from C:/Ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36:in `g
m_original_require'
  from C:/Ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36:in `r
quire'
  from C:/Ruby/lib/ruby/gems/1.8/gems/activesupport-2.3.4/lib/active_supp
rt.rb:56
  from C:/Ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36:in `g
m_original_require'
  from C:/Ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36:in `r
quire'
  from C:/Ruby/lib/ruby/gems/1.8/gems/rails-2.3.4/bin/../lib/rails_genera
or.rb:28
  from C:/Ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36:in `g
m_original_require'
  from C:/Ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36:in `r
quire'
  from C:/Ruby/lib/ruby/gems/1.8/gems/rails-2.3.4/bin/rails:14
  from C:/Ruby/bin/rails:19:in `load'
  from C:/Ruby/bin/rails:19

[解决办法]
gem版本太高，也可以说是rails版本太低，是降低gem版本还是对rails升级就随你了