Bom pessoal abaixo segue o log do erro, onde no caso blog é a sub uri.
I, [2013-12-17T08:27:32.405632 #17145] INFO -- : Started GET "/blog/uploads/post/figura/46/Captura_de_tela.png" for 189.90.133.159 at 2013-12-17 08:27:32 -0200
F, [2013-12-17T08:27:32.408670 #17145] FATAL -- :
ActionController::RoutingError (No route matches [GET] "/uploads/post/figura/46/Captura_de_tela.png"):
actionpack (4.0.1) lib/action_dispatch/middleware/debug_exceptions.rb:21:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
railties (4.0.1) lib/rails/rack/logger.rb:38:in `call_app'
railties (4.0.1) lib/rails/rack/logger.rb:20:in `block in call'
activesupport (4.0.1) lib/active_support/tagged_logging.rb:67:in `block in tagged'
activesupport (4.0.1) lib/active_support/tagged_logging.rb:25:in `tagged'
activesupport (4.0.1) lib/active_support/tagged_logging.rb:67:in `tagged'
railties (4.0.1) lib/rails/rack/logger.rb:20:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/request_id.rb:21:in `call'
rack (1.5.2) lib/rack/methodoverride.rb:21:in `call'
rack (1.5.2) lib/rack/runtime.rb:17:in `call'
activesupport (4.0.1) lib/active_support/cache/strategy/local_cache.rb:83:in `call'
rack (1.5.2) lib/rack/sendfile.rb:112:in `call'
railties (4.0.1) lib/rails/engine.rb:511:in `call'
railties (4.0.1) lib/rails/application.rb:97:in `call'
passenger (4.0.25) lib/phusion_passenger/rack/thread_handler_extension.rb:77:in `process_request'
passenger (4.0.25) lib/phusion_passenger/request_handler/thread_handler.rb:140:in `accept_and_process_next_request'
passenger (4.0.25) lib/phusion_passenger/request_handler/thread_handler.rb:108:in `main_loop'
passenger (4.0.25) lib/phusion_passenger/request_handler.rb:441:in `block (3 levels) in start_threads'