Well, after nearly 4 days I found out what's the problem .. the thing is I am using RAD 8.5 and Websphere portal 8.0 .. while creating my portlet it was created on JSR 168 so the portlet.xml was as follow
http://java.sun.com/xml/ns/portlet/portlet-app_1_0.xsd" id="com.ibm.faces.portlet.FacesPortlet.2a8361a544">
as you can see it uses schema version 1.0
while when I changed it to be
http://java.sun.com/xml/ns/portlet/portlet-app_2_0.xsd" id="com.ibm.faces.portlet.FacesPortlet.2a8361a544">
it worked perfectly fine !
I hope it helps someone out there .. the whole problem was portlet version not compatible with AJAX kind of requests ...