%RUBY_HOME%/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in `gem_original_require': no such file to load -- %RUBY_HOME%/lib/ruby/gems/1.8/gems/mon grel-1.1.2-x86-mswin32-60/lib/mongrel/init.rb (MissingSourceFile) from %RUBY_HOME%/l…

If 0.9.5 is not the answer, do (you may not need to prefix with sudo, on OS X you do, some 窶蕨ix distributions too, but not Windows): sudo gem update --system これが重要