title: Cakephp saveAll continuously giving Array to string conversion error
body: <p>I am developing an Application using 2 models, Users and profiles.
  when I am trying to editing both models at a time, I am getting continuously this error
      <strong>Array to string conversion [CORE\Cake\Model\Datasource\DboSource.php, line 1006]</strong>
  my <code>$this-&gt;request-&gt;data</code> array is in </p>
  
  <pre><code>array(
      'User' =&gt; array(
          'password' =&gt; '*****',
          'id' =&gt; '6',
          'first_name' =&gt; 'some',
          'middle_name' =&gt; 'kjkj',
          'last_name' =&gt; 'one',
          'username' =&gt; 'kadjssa',
          'group_id' =&gt; '5',
          'mobile_no' =&gt; '7867868'
      ),
      'Profile' =&gt; array(
          'skype' =&gt; 'shrinet'
      )
  )
  </code></pre>
  
  <p>and my User controller edit function contain</p>
  
  <pre><code>public function editClient($id = null) {
      $this-&gt;User-&gt;id = $id;
      if (!$this-&gt;User-&gt;exists()) {
          throw new NotFoundException(__('Invalid user'));
      }
      debug($this-&gt;request-&gt;data);
      if ($this-&gt;request-&gt;is('post') || $this-&gt;request-&gt;is('put')) {
  
          $this-&gt;request-&gt;data['User']['user_id'] = $this-&gt;Auth-&gt;User('id');
          $this-&gt;request-&gt;data['Profile']['user_id'] = $id;
  
          debug($this-&gt;request-&gt;data);
          print_r (debug($this-&gt;User-&gt;invalidFields()));
          if ($this-&gt;User-&gt;saveAll($this-&gt;request-&gt;data)) {
              $this-&gt;Session-&gt;setFlash(__('The user has been saved'));
              $this-&gt;redirect(array('action' =&gt; 'index'));
          } else {
              $this-&gt;Session-&gt;setFlash(__('The user could not be saved. Please, try again.'));
          }
      } else {
          $this-&gt;request-&gt;data = $this-&gt;User-&gt;read(null, $id);
      }
      $groups = $this-&gt;User-&gt;Group-&gt;find('list');
      $this-&gt;set(compact('groups'));
  }
  </code></pre>
  
  <p>in debugging its giving</p>
  
  <pre><code>SQL Query: INSERT INTO `mvs`.`users` (`id`, `first_name`, `middle_name`, `last_name`, `username`, `password`, `group_id`, `mobile_no`, `user_id`, `modified`, `created`) VALUES (Array, Array, Array, Array, Array, Array, Array, Array, Array, '2013-07-05 00:07:13', '2013-07-05 00:07:13') 
  </code></pre>
  
  <p>Please help me... thanks in advance</p>