Summary

With backface culling on, the hair completely disappears, indicating the normals are facing the wrong way.  With backface on, the strands reappear but lighting is off.  If you look in the shadow area, for the billboard it's bright instead of dark because it's using the reversed normals for light calculation which is facing towards the light instead of the correct normal, facing away from the light, producing incorrect results.  Max just use the same shading for both side when backface culling is off so it's super important the normal is correct for correct light calculation.  To see this better, you need to use one light instead of the default 2 light viewport max uses.  BTW the light is right above the ball in my example.  

- Tom

still there.