Missing plugin error while building Portlet

[bash]

Following error appears during our Build in Eclipse 3.1

C:\Eclipse\eclipse\plugins\com.webMethods.portal. PortletGenerator_6.5.2.82\lib\build.xml:69: taskdef class com.webMethods.portal.build.GeneratePortletDescriptorBundle cannot be found

Please help

TIA

[bash]

forgot the env details.

wM Portal 6.5