public function subFormIsValid(Zend_Form_SubForm $subForm, array $data)
    {
        ...
-            $this->getSessionNamespace()->$name = $subForm->getValues();
+            $this->getSessionNamespace()->$name = $subForm->getValues(true);
        ...
    }

public function processAction()
    {
        ...
+        $params = $this->getRequest()->getPost();
        if (!$this->subFormIsValid($form,
-                                   $this->getRequest()->getPost())) {
+                                   $params[$form->getName()])) {
        ...
    }

Furthermore there is an issue with Elements of the next SubForm in order beeing displayed as containing erroneous values, though they are displayed for the first time.