Portlets using the OpenPortal JSF portlet bridge stopped working in Liferay 6.1.1 CE GA2, this error occurs:
java.lang.RuntimeException: Unable to unwrap the portlet response from class com.sun.faces.portlet.ViewHandlerPortletRenderResponseWrapper
This is cause by the change of implementation in class com.liferay.portlet.PortletResponseImpl. Previsouly Reflection was used to invoke method getResponse, but this changed to expecting the response object to implement javax.portlet.filter.PortletResponseWrapper. The openPortal portlet bridge do not implement this interface. Since this seem to be the only change in this class I tried to use the class file for com.liferay.portlet.PortletResponseImpl from 6.1.0, and the problem vanished.