OK, I've been on the boards and read as much as I can find. The problem appears to be that the dishwasher doesn't fill completely. I should be getting about 1.5 gallons in the fill cycle but seem to get less than that.

When I add extra water, it seems to run fine, and both upper and lower arms turn.

Here is what I have done so far:

-took off and checked both arms for obstructions -- nothing
-checked the accumulator cover and sump for debris -- nothing
-took off the inlet protector and checked the chopper and screen for debris/obstruction -- nothing
- replaced the sump check valve -- no improvement
- removed the pump assembly and checked the impeller for damage or obstruction -- nothing. Everything turns freely and looks fine.
- checked resistance of the solenoid -- 986 ohms, which is in the range expected.
- took off the fill valve and checked for obstruction -- a couple of small bits of debris. Nothing that looked big enough to impair flow.
- checked water supply line for flow -- plenty.

So.... is there any other reason that there isn't enough water coming in? Should I just replace the fill valve? Comments/suggestions welcome!!

Thanks -- I'll give it a try.