Different model with same problem: the water inlet/drain light flashes. Previous suggestion worked for me in three different situations:
1) The light flashed because there was little water entering. Check the water inlet filter on Miele's external white unit where the water goes in. Unscrew it to remove gunk that had come from our old water tank.
2) The light flashed because the drain and filter inside the machine was blocked. Clean this (regularly) as per the manual. Gunk like rice gets in here. Beware of broken glass. Put it back correctly or else gunk will find its way deeper into the system.
3) The light flashed because the pump system wasn't sending sufficient water through. This also affects the spray arms and washing effectiveness. Do clean the spray arms regularly.
After failing with solution 2 emptying I turned the machine on its side and disconnected pipes near the big pump looking for gunk. The pump is made for easy access. Do try to identify the circulation pipework and don't go disconnecting the water softener unit pipes unnecessarily. I found the problem was caused by a small square piece of bubble wrap which had wrapped itself round the pump impeller. Pure fluke and cheaper that replacing the pump.
Rog F
January 2013