have you taken off the waste pipe from ur u-bend linked to the dishwasher to make sure there is no blockage?...test the waste water function by putting the end of the pipe in a bucket and running a cycle. also check there are no kinks or that the waste pipe isnt flattened behind the appliance. the pipe should travel up from the appliance, and not be too long to the u bend under your sink as this reduces the effectiveness of the appliances ability to get rid of waste water.
andrew
March 2006