Live preview in rails 2.0

I'am trying to set a live preview for my rails app
I using recipe 3 from rails recipies.
It's a recipe from rails 1.0 in 2.0 i get no live preview

in my testapp i have the following code

:controller

def new
  @Post = Post.new
end

def preview
render :layout => false
end

:model
class Post < ActiveRecord::Base
  attr_accessor :title, :body
end

view new.rhtml

<html>
<head>
  <%= javascript_include_tag "prototype"%>
  </head>
  <body>

<% form_for :post, @post, :url=> {:action => 'create', :id =>
"entry-form" } do |f| %>

<%= f.text_field :title %></p>

  <%= f.text_area :body %>
<%= submit_tag "Post" %>
<% end %>

<%= observe_form "post-form",
:update => "live_preview",
:complete => "Element.show('live-preview')",
:url => { :action => "preview" }
%>

<div id="live-preview" style="display: none; border: 1px solid">

</div>

</body>
</html>

:preview.rhtml

<%= textilize params[:page][:body]%>

I got no preview i got nothing.
The only difference in my code and the book i have is into the new.rhtml
because start_form_tag
does not longer exists in 2.0

For now the log gets all the new information from the preview.
But i got nothing on screen only a black line

This is into my log

Processing HomeController#preview (for 127.0.0.1 at 2008-02-01 13:38:28)
[POST]
  Session ID:
BAh7BzoMY3NyZl9pZCIlZDQ0ZGRlMmEwOTIwMzA2OTA3M2UyYTQ2ZWQ0NTU3%0ANTUiCmZsYXNoSUM6J0FjdGlvbkNvbnRyb2xsZXI6OkZsYXNoOjpGbGFzaEhh%0Ac2h7AAY6CkB1c2VkewA%3D--f5e9513b61438c135c515f4e91ff56f0596d1691
  Parameters: {"commit"=>"Post", "post"=>{"title"=>"",
"body"=>"fdfdffddf"},
"authenticity_token"=>"90dfa19958c89b163d86e29bebe88b1bf56fc90a",
"action"=>"preview", "controller"=>"home"}
Rendering home/preview
  Post Columns (0.003355) SHOW FIELDS FROM `posts`
Completed in 0.01117 (89 reqs/sec) | Rendering: 0.00172 (15%) | DB:
0.00336 (30%) | 200 OK [http://0.0.0.0/home/preview]

In my view i have this

<%= observe_form "post-form",
:frequency => 1,
:update => "live_preview",
:complete => "Element.show('live-preview')",
:url => { :action => "preview" }
%>

<div id="live-preview" style="display: none; border: 1px solid"></div>

but the div gives no result of the preview method