you need to establish whether the water is coming from the incoming supply, or coming back from the sink waste.
as in recent years quick fit plumbing has been fitted to the waste in many houses, these are quite often poorly installed, and water drains back into the machine.
try turning off the incoming water to the appliance from the two little taps which should be behind the machine.
If this cures the problem, you probably have a faulty water valve. there are 2 on most appliances, and I would then try to identify whether the problem is with the hot or cold valve by repeating the last step individually with each tap.
Paul
August 2004