before having to go to the extremes of draiins, try this.....
run on hot wash (90C) with nothing in the machine except a bit of white vinegar in the drum.
ive not actually tried this myself as i dont have that problem, but ive heard it said a few times by various people. i thought it a bit odd at first, but thinking about it, the worst it can do is waste a bit of vinegar, as no clothes in the machine to get ruined :)
hope this helps
tony, January 2009