Inconsistent REST behavior

Has anyone seen Rails save nested associations despite their being

If I hit the site from a different Rails app (using ActiveResource)
and try to update the record so that the username is too short it
fails (as I expect) and adds an errors attribute to the object that I
can inspect. The original account (and associated user and email
objects) is unaffected, as I'd expect.

Hitting the same exact URL with a raw HTTP/REST client and sending in

<?xml version="1.0" encoding="UTF-8"?>


It gives me the expected 422 Unprocessible Entity error, which I
expect. However it also saves user down as a null! That I do not

My question is why does it correctly handle errors with ActiveResource
(eg. doesn't save anything down since their are validation problems)
but with a raw PUT request it saves with a null user object
(effectively killing the user).

# models

class User < ActiveRecord::Base
  belongs_to :account

  validates_length_of :username, :minimum => 6


class Account < ActiveRecord::Base

  has_one :user
  has_one :email

  has_many :account_entitlements
  has_many :entitlements, :through => :account_entitlements

  accepts_nested_attributes_for :user, :email

  def user=(params)
    update_attributes(:user_attributes => params)

  def email=(params)
    update_attributes(:email_attributes => params)


# controller

  def update
    @account = Account.find(params[:id])

    respond_to do |format|
      if @account.update_attributes(params[:account])
        flash[:notice] = 'Account was successfully updated.'
        format.html { redirect_to(@account) }
        format.xml { head :ok }
        format.html { render :action => "edit" }
        format.xml { render :xml => @account.errors, :status
=> :unprocessable_entity }