Following up my previous answer. I found 2 colour catcher sheets in the black drain pipe next to the pump, needless to say we have stopped using them now. It was easy to clear the pipe. The pump is on the bottom right as you look from the back of the machine
Make sure you disconnect the power supply.
Remove 2 white plastic clips which clamp external drain pipe and black pipe to pump.
Undo 2 metal jubilee clips on black pipe and remove pipe.
inside you will find the item causing trouble.
Ian, February 2010