添加控制器后,WEBrick启动失败,请帮忙解答

添加控制器后,WEBrick启动失败,提示如下:
C:\php?name=rails" onclick="tagshow(event)" class="t_tag">railspro\hello>ruby script/server
=> Booting WEBrick...
d:/Ruby/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/dependenci
es.rb:428:in `load_missing_constant': Expected C:/railspro/hello/app/helpers/app
_helper.rb to define AppHelper (LoadError)
   from d:/Ruby/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_suppo
rt/dependencies.rb:77:in `const_missing'
   from d:/Ruby/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_suppo
rt/dependencies.rb:89:in `const_missing'
   from d:/Ruby/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_suppo
rt/inflector.rb:352:in `constantize'
   from d:/Ruby/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_suppo
rt/inflector.rb:351:in `each'
   from d:/Ruby/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_suppo
rt/inflector.rb:351:in `constantize'
   from d:/Ruby/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_suppo
rt/core_ext/string/inflections.rb:162:in `constantize'
   from d:/Ruby/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controll
er/helpers.rb:133:in `helper'
   from d:/Ruby/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controll
er/helpers.rb:111:in `each'
   ... 38 levels...
   from d:/Ruby/lib/ruby/gems/1.8/gems/rails-2.2.2/lib/commands/server.rb:4
9
   from d:/Ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `ge
m_original_require'
   from d:/Ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `re
quire'
   from script/server:3