ActionController::RoutingError (uninitialized constant User::UsersController) in heroku (but everything works in local)

I am trying to run my app in heroku but I get this error when trying to signup or even access devise's login page:

ActionController::RoutingError (uninitialized constant User::UsersController)

Is this a devise bug or a server setting i missed in heroku?

I am running a rails3.1 app in a cedar stack by the way and loading the index page is good, but if I try to login or sign up, it blows.

The signup form DOES show, but when I submit, that's when it blows. I checked the logs and it did POST to the controller but GETting the resulting page(when redirected I guess) blows it up.

Any help?

EDIT

here are my routes:

root :to => "home#index"

devise_for :users

namespace :user do
  root :to => "users#welcome"
end

resources :users, :only => :show

A heroku support person also asked about my routes but why does it happen in production only? Also I don't think there's any problem with the routes...is there?

Solution

This is your problem:

namespace :user do
  root :to => "users#welcome"
end

Can you remove this?