I had same problem.. Actually my problem was form was not posting.. postAction () was not being called.. and after a long struggle… I got the solution..
Try adding this on the form..
<input name="form_key" type="hidden" value="<?php echo Mage::getSingleton('core/session')->getFormKey() ?>" />
this is by adding on the .phtml file… and while you generate form by code… the try this
$this->_objectId = 'id';
It worked for me.. :D