I had that with my Bosch machine. I put it down to mainly using the quick wash (as the machine took about 2 hours to wash on a full cycle!) it was grey sludgy stuff which came thru the holes inside the washer and was all over the clothes. Really annoying! It was a build up of soap because i was only using the quick wash. Every couple of weeks i now 'clean' the machine with 1/2 pint of white vinegar and a good squirt of lemon juice, and run the machine on its own with no clothes on a hot long wash, this did the trick! Hope this helps you. Good luck and let me know!
Janice
November 2009