Did you also use the latest SNAPSHOT Eclispe plugins?
http://hudson.jboss.org/hudson/job/drools/lastSuccessfulBuild/artifact/target/drools-5.2.0-SNAPSHOT-eclipse-all.zip
http://community.jboss.org/servlet/JiveServlet/download/15922-4-18524/jbpm-5.0-SNAPSHOT-eclipse-all.zip
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