Why is unity crashing when I import an FBX file exported from maya?

My unity proyect is crashing when i try to import the FBX file previously exported from Maya, and it gives me this error

NullReferenceException: Object reference not set to an instance of an object UnityEditor.AssetImporterInspector.get_targetName ()

I have the same rigged model but with other animation in a different .mb file and if I export that one as FBX there is no problem, but when i try this one where the animation comes from an bvh file then i have this problem, i've plot the animation to the bones but its still not working.

Thanks