How can I get my Maytag JetClean dishwasher EQ+ to complete wash cycles?

I have a 2002 Maytag JetClean EQ+ dishwasher that has worked fairly well until recently. When I initiate any wash cycle, it fills with water and begins washing. But a short time later (maybe 5 to 15 minutes into the cycle), it stops washing even though the control panel lights remain on and the timer continues counting down to the end of the cycle and the "clean" light comes on even though the dishes are not clean. A couple consistent observations: When we repeat the same cycle several times, the cycle always stops at the same time: for instance, the "light wash" cycle starts at 85 minutes and continues washing as it should until it reaches 70 minutes, at which time it always stops (even though the display timer continues counting down to the end of the cycle). Also, when I push the "drain" button to manually drain, it won't drain. I'm grateful for any ideas...thanks.