What's an effective approach to debug NameErrors in Rails?

I'm trying to use the desert plugin (0.5.0) and the edge version of Community_Engine. I've started from scratch and gone through the installation instructions. When I attempt to start my server, I get this error: "Constant RAILS_END from rails_end.rb not found (NameError)". Problem is I cannot find rails_end.rb, nor can I find a google reference to this file or error.

I've verified that the required gems are installed and current. I've dug around google and desert, but haven't found any reference to this constant.

Any ideas? Thanks

Here's my stack trace:

=> Booting Mongrel
=> Rails 2.3.2 application starting on http://0.0.0.0:3000
/opt/local/lib/ruby/gems/1.8/gems/desert-0.5.0/lib/desert/rails/
dependencies.rb:15:in `load_missing_constant': Constant RAILS_END from
rails_end.rb not found (NameError)
       from /Users/dmr/.gem/ruby/1.8/gems/activesupport-2.3.2/lib/
active_support/dependencies.rb:80:in `const_missing'
       from /Users/dmr/.gem/ruby/1.8/gems/activesupport-2.3.2/lib/
active_support/dependencies.rb:92:in `const_missing'
       from /Users/dmr/dev/lionfold/config/environment.rb:32
       from /Users/dmr/.gem/ruby/1.8/gems/rails-2.3.2/lib/
initializer.rb:111:in `run'
       from /Users/dmr/dev/myapp/config/environment.rb:31
       from /opt/local/lib/ruby/vendor_ruby/1.8/rubygems/
custom_require.rb:31:in `gem_original_require'
       from /opt/local/lib/ruby/vendor_ruby/1.8/rubygems/
custom_require.rb:31:in `require'
       from /Users/dmr/.gem/ruby/1.8/gems/activesupport-2.3.2/lib/
active_support/dependencies.rb:156:in `require'
       from /Users/dmr/.gem/ruby/1.8/gems/activesupport-2.3.2/lib/
active_support/dependencies.rb:521:in `new_constants_in'
       from /Users/dmr/.gem/ruby/1.8/gems/activesupport-2.3.2/lib/
active_support/dependencies.rb:156:in `require'
       from /Users/dmr/.gem/ruby/1.8/gems/rails-2.3.2/lib/commands/
server.rb:84
       from /opt/local/lib/ruby/vendor_ruby/1.8/rubygems/
custom_require.rb:31:in `gem_original_require'
       from /opt/local/lib/ruby/vendor_ruby/1.8/rubygems/
custom_require.rb:31:in `require'
       from script/server:3