sounds as if you have a leak from the dishwasher, there is an anti flood device on the unit, if water leaks from the unit it collects in the plastic trough below the unit, when it gets to a certain height, a float switch cuts in the pump and shuts down the operation of the unit until the water is removed, the only way to stop the pump is to switch off at the mains.
We got an expert to look at the unit, after taking the side off he sponged out the water and identified the leak from the joint between the innercasing of the unit and sealed it.
This lasted a year till it started again, when it was identified as major pump leak and disposed of.
Paul Dancer, April 2006