map.resources helpers not recognized in production only

I've got a 'map.resources :ultra_things' in my routes.rb, and in a view I have...

<%= link_to @ultra_thing.name, ultra_thing_path(@ultra_thing.id) %>

And this all works very, very well.... in development.

However, on the production server I get an error in the log...

(undefined method `ultra_thing_path' for #<#<Class:0xb7504050>: 0xb7504028>) on line #5 of app/views/ultra_things/list.rhtml

They're both using the exact same code (deployed from trunk with capistrano). They're both running on the same version of Rails (1.2.3).

What the **** am I missing? I running out of hair fast here.