"ActionView::TemplateError" "wrong argument type" "expected Proc"

I updated Ruby 1.8.6 (the version recommended on http://www.rubyonrails.org/down ) to the patch level recommended on

http://www.ruby-lang.org/en/news...

  $ ruby -v
  ruby 1.8.6 (2008-06-20 patchlevel 230) [i686-linux]

Updating Rails to 2.1.0 brought this:

$ ./script/server -e test -p 2000
=> Booting Mongrel (use 'script/server webrick' to force WEBrick)
=> Rails 2.1.0 application starting on http://0.0.0.0:2000
[...]
ActionView::TemplateError (wrong argument type String (expected Proc)) on line #21 db:structure:dump broken by 8a5a9dc of list/index.html.erb:
18: <div>
19: <h3>Add list</h3>
20: <%= error_messages_for :list %>
21: <% form_for :list, @list, :url => {:action => "create"} do |f| %>
22:   <div>
23:     <%= label(:list, :name) %>
24:     <%= f.text_field :name, :size => 22 %>

    (eval):2:in `protect_against_forgery?'
    /usr/local/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/action_view/helpers/form_tag_helper.rb:431:in `extra_tags_for_for