cannot use link_to helper

[matsubo]

After I restarted Webrick server, I've got following permanent error so If you have time, please fix the issue.

In order to use #url_for, you must include routing helpers explicitly. For instance, `include Rails.application.routes.url_helpers

I uploaded the screenshot on the following url. http://www.flickr.com/photos/matsubokkuri/6229525161/

The page is generated by scaffolding and nothing to do special.

If I remove sitemap-generator plugin and restart the server, the error is not shown.

Using packages are following . The error occurs on Mac OS X Lion and Snow Leopard.

% bundle
Using rake (0.9.2) 
Using multi_json (1.0.3) 
Using activesupport (3.1.0) 
Using bcrypt-ruby (3.0.1) 
Using builder (3.0.0) 
Using i18n (0.6.0) 
Using activemodel (3.1.0) 
Using erubis (2.7.0) 
Using rack (1.3.4) 
Using rack-cache (1.0.3) 
Using rack-mount (0.8.3) 
Using rack-test (0.6.1) 
Using hike (1.2.1) 
Using tilt (1.3.3) 
Using sprockets (2.0.1) 
Using actionpack (3.1.0) 
Using mime-types (1.16) 
Using polyglot (0.3.2) 
Using treetop (1.4.10) 
Using mail (2.3.0) 
Using actionmailer (3.1.0) 
Using arel (2.2.1) 
Using tzinfo (0.3.30) 
Using activerecord (3.1.0) 
Using activeresource (3.1.0) 
Using bundler (1.0.18) 
Using coffee-script-source (1.1.2) 
Using execjs (1.2.9) 
Using coffee-script (2.2.0) 
Using rack-ssl (1.3.2) 
Using rdoc (3.9.4) 
Using thor (0.14.6) 
Using railties (3.1.0) 
Using coffee-rails (3.1.1) 
Using jquery-rails (1.0.14) 
Using json (1.6.1) 
Using mysql2 (0.3.7) 
Using rails (3.1.0) 
Using sass (3.1.8) 
Using sass-rails (3.1.4) 
Using sqlite3 (1.3.4) 
Using uglifier (1.0.3)