I faced such a problem. I have created a custom portlet and tryed to submit form from jsp page to processAction method.
<form method="POST" name="PortletPersonalizeForm" action="<portlet:actionURL/>" charset="UTF-8" >
The result of this
java.lang.ClassCastException: za.hp.ppm.ini.InitPortlet cannot be cast to javax.portlet.Portlet
I'am not strong with deploying portlets at PPM, so any help would be appreciated