OK, that explains the weirdness about the pink screens.
I checked over my code before I sent it out for you to look at and discovered that I had made the answer into a Formula after all. (sigh) So, I withdraw my question about the exponentiation.
Still, I didn't know that fun_cmp would work with MathObjects. I remember trying to use PG answer evaluators with a MathObject a month or so ago and got errors. I'm attaching the code anyway. It's not a big deal, but since I am using MathObjects, I think it would work nicer with a List instead of the array I'm using--any advice?