Can you paste the bpmn2 of your simple process you created with Designer that creates the "no interfaces found" error (while working on the process you can view it's source in the Guvnor tab go to Source->View Source)?
jbpm-console currently looks at defaultPackage only. You would have to put all your processes in Guvnor's defaultPackage and make sure your processes specify the same in the package attribute. Ability for jbpm-console to look up processes in all packages has just been added in master via https://issues.jboss.org/browse/JBPM-3320.