Tim,
When I click on the OK button of the Transformator dialog, sometimes it takes a long time for Muse to select all the filtered events, especially if there are a lot of midi tracks, and "process all events" is checked. But there's no visual feedback to show that Muse is "busy". I thought that it was continually locking up at first, Maybe a "Please wait..." or "Processing..." message would be good to show during this phase.