I have an MVC3 project that uses Ninject, Entity Framework and the Unit of Work pattern with a Service layer.
My AsyncService class has a function that starts a back
InRequestScope'd objects are Disposed at the end of a request so it can't be used in this case. InThreadScope also doesn't fit as that would reuse the UoW for several tasks.
What you can do though is declare your AsyncService as the Scoping Object for all the objects within using the NamedScope extension.
See http://www.planetgeek.ch/2010/12/08/how-to-use-the-additional-ninject-scopes-of-namedscope/