Look - I'm sorry about this - I know very little about these appliances but when this last happened to me the smell was coming from the drains. They had become blocked and foul water was backing up in the pipes.
Our Wm/c had no S-bend in the drain and this allowed the horrible smell into the house.
You can test for this by flushing a downstairs toilet - if the water rises further up the pan than is usual and then slowly recedes then you have a blocked drain and that's the cause of the smell.
You may have an inspection pit outside - where the drains all meet.
If this is not the case then I apologise for wasting your time - best probably to put your question in again and I'll keep well away from it and let an expert give an answer.
Good luck...
Peccavi, April 2013
