Hi Tommy, I think you are using an older version of Designer. Can you please re-try with latest from sourceforge: http://sourceforge.net/projects/jbpm/files/designer/designer-1.0.0.054/ (get designer-1.0.0.054-jboss.war and rename to designer.war before deploying). A fairly recent change we made to the bpmn2 impl to to change the structureRef attribute to be type string rather than an actual reference, to follow how jBPM expects it.
Hope this helps.