Cliff, thanks for the reply.
I suppose I should have added the disclaimer that I'm not working in Flex so I don't have IDs for my windows "out of the box" so to speak. I suppose I'll implement this and assign IDs to windows when they're created and use your suggestion of using this value for the mediator. Of course if I had multiple windows going at once that had the same IDs, could there be name collisions (when removing or registering)?
Finally, thanks for all your work on the framework and your ongoing support here