Error Metodo de pago Multibanco

[cunharic]

Buenas noches,
Estoy utilizando la extension de pago de ifthen para multibanco.
Al intentar editar y guardar un pedido me sale el siguiente error:

There has been an error processing your requestCannot send headers; headers already sent in /home/cantinho/public_html/app/code/community/Mage/MultibancoPayment/Helper/Data.php, line 12
Trace:
#0 /home/cantinho/public_html/lib/Zend/Controller/Response/Abstract.php(148): Zend_Controller_Response_Abstract->canSendHeaders(true)
#1 /home/cantinho/public_html/app/code/core/Mage/Adminhtml/Controller/Action.php(398): Zend_Controller_Response_Abstract->setRedirect('http://www.cant...')
#2 /home/cantinho/public_html/app/code/core/Mage/Adminhtml/controllers/Sales/Order/CreateController.php(396): Mage_Adminhtml_Controller_Action->_redirect('*/*/')
#3 /home/cantinho/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Mage_Adminhtml_Sales_Order_CreateController->saveAction()
#4 /home/cantinho/public_html/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('save')
#5 /home/cantinho/public_html/app/code/core/Mage/Core/Controller/Varien/Front.php(177): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#6 /home/cantinho/public_html/app/code/core/Mage/Core/Model/App.php(304): Mage_Core_Controller_Varien_Front->dispatch()
#7 /home/cantinho/public_html/app/Mage.php(596): Mage_Core_Model_App->run(Array)
#8 /home/cantinho/public_html/index.php(78): Mage::run('', 'store')
#9 {main}

y no me emite el nuevo pedido.
Como lo puedo solucionar?
Un saludo
Muchas gracias
Ricardo
Cantinho das Fotos