Ninject + Bind generic repository
Solution 1:
Bind(typeof(IRepository<>)).To(typeof(Repository<>));
This is the correct syntax for binding an open generic.
If you are receiving null back when requesting IRepository< of whatever >, then there may be some other problem in an area of code you haven't shared.
Solution 2:
See my answer on MVC3 Controller constructor + Ninject.
Generic Binding works correctly in Ninject. Try using a parameterless constructor in Repository. I think the problem is there.