I took it all apart, right on down to the pump and impeller. When I started to clean up every part, I noticed that the upper feed tube had a crack in it near the bottom of the tub. This prevented water from going into the spray arms, and probably reduced the pressure going to the lower arm, causing it not to spin and wash. So I continued cleaning every part, channel, gasket, tube, etc, found that I also needed a filter basket, for a minor reason. I got the upper feed tube in a couple days, put the whole machine back together, and ran a load of dishes. Now everything gets cleaned and it all seems to work fine. Funny how a simple breakage could cause the whole thing to malfunction like it did.