Flex + Rails + Mysql Database Error

Hi,
  I am integrating flex front end with rails back end. I am simply
using XML formatted data.

If there is some data in the database then i am able to generate xml
data through rails. and using HTTPServices i am displaying this xml
data in flex front end using datagrid.

But when i want to insert some records in database it throws me an
error

[RPC Fault faultString="HTTP request error"
faultCode="Server.Error.Request" faultDetail="Error: [IOErrorEvent
type="ioError" bubbles=false cancelable=false eventPhase=2 text="Error
#2032: Stream Error. URL: http://localhost:3000/reviews/create"]. URL:
http://localhost:3000/reviews/create"]

HTTPService:

<mx:HTTPService contentType="application/xml"
id="reviewCreateRequest"
                    url="http://localhost:3000/reviews/create"
                    useProxy="false" method="POST">
        <mx:request xmlns="">
            <review>
                <title>{fTitle.text}</title>
                <author>{fAuthor.text}</author>
                <score>{fScore.text}</score>
                <text>{fText.text}</text>
            </review>
        </mx:request>
    </mx:HTTPService>

my controller looks like :

class ReviewsController < ApplicationController
def
list
      @reviews = Review.find :all
      render :xml => @reviews.to_xml
    end
def create
      @review = Review.new(params[:review])
      @review.save
      render :xml => @review.to_xml
    end
end

I saw the rails log file. The xml data is which i am sending to
database is there but cant write it to the database

Log file

Processing ReviewsController#create (for 127.0.0.1 at 2008-02-22
01:17:05) [POST]
  Session ID:
BAh7ByIKZmxhc2hJQzonQWN0aW9uQ29udHJvbGxlcjo6Rmxhc2g6OkZsYXNo
%0ASGFzaHsABjoKQHVzZWR7ADoMY3NyZl9pZCIlYjUzYzJjZWQ3MjA2YWE3ZjE2%0AZWU4MGU3OWYwYzllOTI
%3D--4d18c41667e30a8839a800fad2701d4b0c6303c6
  Parameters: {"review"=>{"score"=>"123", "text"=>"jkjfdfdf",
"title"=>"RoR", "author"=>"XYZ"}, "action"=>"create",
"controller"=>"reviews"}
.
.
.
Rendering c:/ruby/lib/ruby/gems/1.8/gems/actionpack-2.0.2/lib/
action_controller/templates/rescues/layout.erb (unprocessable_entity)

I am following the same tutorial given here
http://www.liverail.net/articles/2006/4/16/rubyonrails-1-1-and-flex-2-0-pt-1

Is this a problem due to new rails version?

Any suggestion regarding this will be appreciated
Thanks in advance
Mukesh sahu