Are people sick of reflection questions yet? ;-)

I started playing with reflections using the old Bryce standby - a couple of spheres hovering over a reflective surface. (I was going to try water later on.) I used the basic reflection settings in the Alternate_Diffuse channel on the Square - Hi Res. I rendered it in firefly. (Picture on left.) The basic settings looked okay, though only 1 sphere out of three reflected. (Maybe the other 2 are too far up, though that seems weird to me.)

When I turned on the Cast Shadow property, I got ugly jaggies in the reflection. (Picture on right.) Am I doing something wrong? I've tried changing the Minimum Shading Rate, etc. Only "Cast Shadows" makes the jaggies as far as I can tell, and nothing seems to fix it. I've tried other combinations, and only the "Cast Shadows" seems to cause the issue, but it looks wrong to not have shadows. Also, why are the other 2 spheres not reflecting? (They're only 1.6 feet up.)

Thanks for any/all assistance!