Hopefully this helps others.
1. Before installing (ant install.demo.noeclipse), modify $JBPM_HOME/build.xml file with the ports you'd like JBoss to run on.
2. Ensure all environment variables are set properly and directories exist before trying to start.
3. Reinstall jbpm with ant clean.demo; ant install.demo.noeclipse. NOTE: this removes the entire jboss sub-directory, so any modifications you've made will be removed.