This code works fine:
class UsuariosCadastrarForm extends SGCI_Form {
	
	function __construct($options = null) {
		
		parent::__construct($options);
		
		$this->setMethod('post')
        	 ->setAttrib('id', 'login');
        	 
	       	$div = new Zend_Form_Element('div', array('disableLoadDefaultDecorators' => true));
	        $div->addPrefixPath('CBr_Form_Decorator', 'CBr/Form/Decorator/', 'decorator');
	        $div->addDecorator('Div', array('id' => 'dv'));
        
	        $this->addElements( array (
		        $div,
	        ));
	}
}