what is the version of eclipse?
what is the version of the plugin?
Eclipse Version: 3.1.0
and JBPM plugin is 3.0.8 (jbpm-gpd-site-3.0.8)
will this combination cause any problem?
Did you go through the installation process successfully? It is a combination that should work and it looks like WTP was not installed correctly. Do you have other plugins installed?