Help in resolving : failed to load or instantiate TagExtraInfo class org.apache.pluto.tags.DefineObjectsTag

Hi, I'm new to Pluto portal development and I'm facing the below error when 
I build pluto-portal.war in Netbeans. After much a try I have successfully 
deployed and tested Portal, except few pages are not showing up due to the 
below error.  Need your expert suggestion to solve the error.

Source :
******
view.jsp
<%@ taglib uri="http://java.sun.com/portlet" prefix="portlet" %>

web.xml
  <taglib>
    <taglib-uri>http://java.sun.com/portlet</taglib-uri>
    <taglib-location>/WEB-INF/tld/portlet.tld</taglib-location>
  </taglib>


Error: Failed to load or instantiate TagExtraInfo class: 
org.apache.pluto.tags.DefineObjectsTag$TEI

Configuration:
Netbeans : 6
JDK  : 1.5
Server : Glassfish

Regards,
Leo