Namespaced controller sometimes uses default layout, views

This is quite elusive bug, happened twice on production but I wasn't able to reproduce it in development environment yet.

I have two SessionControllers. One is used for site patrons, is available under /sessions and uses application.html.haml layout. Another for admin login, is available under /admin/sessions and uses admin/administration.html.haml layout.

When server runs for some time namespaced controller starts to use application layout instead of administration one and renders views from app/views/sessions rather than app/views/admin/sessions. After server restart everything goes back to normal.

Relevant code snippets:

config/routes.rb

  map.namespace :admin do |admin|
    admin.resource :session
  end
  # snip...
  map.resources :sessions, :collection => {:admin_new => :get,
    :admin_create => :post, :auto_complete_for_user_email => :get}

app/controllers/admin/admin_controller.rb

class Admin::AdminController < ApplicationController
  layout 'admin/administration'
  before_filter :require_admin

  def index
  end
end

app/controllers/admin/sessions_controller.rb

class Admin::SessionsController < Admin::AdminController
  skip_before_filter :require_admin
end

Snippet from production.log

Processing AdminController#index (for 84.186.212.124 at 2008-09-15 10:55:18) [GET]
  Session ID: BAh7CzoMdXNlcl9pZDA6DnJldHVybl90bzA6DGNzcmZfaWQiJTU1NTZlYmI5
N2JkODdhMjlkZjZhYjhmZmFiZTI0YmEyOg1hZG1pbl9pZDAiCmZsYXNoSUM6
J0FjdGlvbkNvbnRyb2xsZXI6OkZsYXNoOjpGbGFzaEhhc2h7BjoKZXJyb3Ii
L0NvdWxkbid0IGxvZyB5b3UgaW4gYXMgJ2FkbWluQGV4YW1wbGUuY29tJwY6
CkB1c2VkewY7CkY6FGFkbWluX3JldHVybl90byILL2FkbWlu--197369dabe2c5f5e1ca0a02f1dbbae997ba76058
  Parameters: {"action"=>"index", "controller"=>"admin/admin"}
Redirected to http://beta.jobmensa.de/admin/session/new
Filter chain halted as [:require_admin] rendered_or_redirected.
Completed in 0.00692 (144 reqs/sec) | DB: 0.00168 (24%) | 302 Found [http://beta.jobmensa.de/admin]


Processing SessionsController#new (for 84.186.212.124 at 2008-09-15 10:55:18) [GET]
  Session ID: BAh7CzoMdXNlcl9pZDA6DnJldHVybl90bzA6DWFkbWluX2lkMDoMY3NyZl9p
ZCIlNTU1NmViYjk3YmQ4N2EyOWRmNmFiOGZmYWJlMjRiYTIiCmZsYXNoSUM6
J0FjdGlvbkNvbnRyb2xsZXI6OkZsYXNoOjpGbGFzaEhhc2h7BjoKZXJyb3Ii
L0NvdWxkbid0IGxvZyB5b3UgaW4gYXMgJ2FkbWluQGV4YW1wbGUuY29tJwY6
CkB1c2VkewY7ClQ6FGFkbWluX3JldHVybl90byILL2FkbWlu--350d8cc6aa7eb2fcca080b9f74646b44132e1215
  Parameters: {"action"=>"new", "controller"=>"admin/sessions"}
Rendering template within layouts/application
Rendering sessions/new
Rendering page snippet: Layout footer contents (0.00396)
Rendering page snippet: Layout footer links (0.00382)
Completed in 0.08378 (11 reqs/sec) | Rendering: 0.07137 (85%) | DB: 0.00899 (10%) | 200 OK [http://beta.jobmensa.de/admin/session/new]

Site runs on mongrel 1.1.5 and Ruby on Rails 2.1.0