Hi Mark,
The cause of the problem is a gummed-up water level float chamber (part #13 in the diagram click here). You need to pull it out, clean it, and put it all back together and the dishwasher should run fine.
You might need help of a handy person to do this. See picture below.
Pull the entire dishwasher out and lay it down on its side (facing the door, tip it over to your right):
Inside that little box with all the sediment and glop is a wing-shaped float that couldn't move due to the glop. Simply held the whole plastic thing under the sink faucet to rinse it out. You have to take off the tub pan in order to pull off the drain hose that's attached to the back of this chamber. After rinsing it out, put it back in and the dishwasher should be running fine.
Let me know if this helps.