At the start of a cycle, the dishwasher pumps out and fills, but then just hums (no pumping action through the spray arms) until it pumps out and refills again , and so on until the timer dial goes around and completes the "wash" (or non-wash). The heating element seems to work properly. The dw was just reactivated – it was protected with RV type antifreeze over a 5-month winter break – fourth year in a row, and this is the first spring where we had a problem.
Ah, I found the answer searching the "Knowledge Base" of GEAppliances.com – to summarize, when there is a hum from the motor it indicates the pump seals stuck during the winter layover and the fix is to mix up a solution of citric acid and water or one cup white vinegar to a quart of hot water and pour it down through the power tower in the center of the spray arm, let it stand for approx. 30 minutes and run the dishwasher through one complete cycle. It worked like a charm and the dw is merrily washing away.