please verify that the following lines are found in standalone.xml in JBoss/standalone/configuration directory .
<security-domain name="jbpm-console" cache-type="default">
<authentication>
<login-module code="UsersRoles" flag="required"/>
</authentication>
</security-domain>
and also there shoule be a datasaource defined for jbpmDS
I had the same problem outside of jbpm demo when i deployed them seperatly.