Server is broken!

The mongrel server has mysteriously stopped working on one of my rails
projects.

Here's what the console says:

$ script/server => Booting Mongrel (use 'script/server webrick' to
force WEBrick)
=> Rails 2.1.0 application starting on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server
** Starting Mongrel listening at 0.0.0.0:3000
** Starting Rails with development environment...
Exiting
/Library/Ruby/Gems/1.8/gems/activesupport-2.1.0/lib/active_support/
dependencies.rb:492:in `const_missing': uninitialized constant
Rails::Plugin::Err (NameError)
  from /Users/mark/Sites/rubyonrails/rails_space/vendor/plugins/plugins/
acts_as_cached/init.rb:2:in `evaluate_init_rb'
  from /Library/Ruby/Gems/1.8/gems/rails-2.1.0/lib/rails/plugin.rb:
95:in `evaluate_init_rb'
  from /Library/Ruby/Gems/1.8/gems/activesupport-2.1.0/lib/
active_support/core_ext/kernel/reporting.rb:11:in `silence_warnings'
  from /Library/Ruby/Gems/1.8/gems/rails-2.1.0/lib/rails/plugin.rb:
91:in `evaluate_init_rb'
  from /Library/Ruby/Gems/1.8/gems/rails-2.1.0/lib/rails/plugin.rb:
44:in `load'
  from /Library/Ruby/Gems/1.8/gems/rails-2.1.0/lib/rails/plugin/
loader.rb:33:in `load_plugins'
  from /Library/Ruby/Gems/1.8/gems/rails-2.1.0/lib/rails/plugin/
loader.rb:32:in `each'
  from /Library/Ruby/Gems/1.8/gems/rails-2.1.0/lib/rails/plugin/
loader.rb:32:in `load_plugins'
   ... 31 levels...
  from /Library/Ruby/Gems/1.8/gems/rails-2.1.0/lib/commands/server.rb:
39
  from /Library/Ruby/Site/1.8/rubygems/custom_require.rb:27:in
`gem_original_require'
  from /Library/Ruby/Site/1.8/rubygems/custom_require.rb:27:in
`require'
  from script/server:3

I'm stumped, any ideas?

Thanks!

Seems to me you have either missing plugins or plugin incompatibility.

Thanks for your suggestion, how can I check this and fix it?

Remove acts_as_cached from the plugins folder (since the stack trace points to that plugin if you read carefully) and try to start the server again. If the error doesn’t occur, you have the choice of trying to make that plugin work with your Rails version by patching it or searching for an alternative.

BTW, if you’re using Rails 2.1, I believe that plugin is totally unnecessary, since Rails has memcached support built-in. Search google for more info on Rails 2.1 caching.