How do i clear the Ensemble Workflow Tasklist

Hello-

I am working on an Ensemble demonstration that involves workflow.  Over the course of testing I have cleared out the Ensemble message store several times.  This has left several workflow tasks that no longer can be assigned, accepted or rejected.

How do I clear the Workflow Tasklist which is found by going to Ensemble -> Manage -> Workflow -> Workflow Tasks in the Ensemble Management Portal?

Thanks in advance

Ken