It might be this... but then again it might not be...
In the very bottom of the internal sump, under the filters, you may find a single Torx screw. If you remove it you get access to the impeller of the drain pump. Sometimes crud gets trapped under the blades. Tweezers may help in the removal. The impeller blades should move freely but with a bit of magnetic resistance.
It worked for me on my Bosch DW
Good luck...
Peccavi, July 2009