2D Animation Clip created in Unity, can't use as Motion in Animator

After watching the Unity 2D video explaining their example, and reading around for a couple of hours, I can't figure out how to get this to work.

I created a character with a similar layout to the hero in the Unity 2D example. I used the built in animator to create a couple of clips, which I can preview in the inspector and looks great. I added an Animator component with a new controller, but in the controller I cannot use my clips as the Motion in the animation states. It gives the following error : " Animation clips used within the Animator Controller need to have Muscle Definition set up in the Asset Importer Inspector".

Can anyone point me in the right direction with what I need to do, or tell me what I'm doing wrong? The only thing I notice is that the clips from the 2D example look slightly different in the inspector, but even with those I don't see anything about Muscle Definition.

Edit: Nevermind, reinstalling Unity allowed new clips I made to work properly. Maybe I installed it over the previous version or it didn't update properly, whichever. All good now!