How can I fix our Hotpoint FDW20P dishwasher?

How can I fix our Hotpoint FDW20P dishwasher? It didn't empty at the end of its cycle and a small amount of water escaped over the floor. I pulled the machine out, ran the waste hose out through the door and it drained ok. I cleaned filters, checked the hose and ran a couple of rinse cycles - the machine emptied fine and worked ok for a couple of washes. Suddenly it has done the same thing again, failed to empty with resulting leakage over the floor.