MVC :: Routing Error On Default Route In Virtual Directory?

I have an application that I run in several places (demo, production, local, etc.) that all use different virtual directories for the placement of the MVC application.

I use StructureMap in this application, so I am overriding the ControllerFactory to use StructureMap to build controllers (when the passed controller instance is not null).

My problem is that the controller instance being passed to the controller factory IS null, which is fine if said route didn't exist, but it does... specifically, it should be my DEFAULT ROOT route.

Basically if I host the app at [URL], everything works fine except when I have a '/' on the end of the URL (meaning,[URL]... the latter works fine, while the former gives me the error). It looks like when that slash is there, the routing engine is deciding that it should be looking for a controller named MvcController, which doesn't exist, and which then passes the null controller instance to the ControllerFactory, resulting in the following error:

The controller for path '/Mvc/' could not be found or it does not implement IController.
My Default route is the standard default route. Removing all other routes has no effect. My default controller is HomeController.