I couldn't agree more - that, often, those menial tasks (washing dishes, doing laundry, or even just "being quiet" for a bit) relax my brain enough to let brainstorming in. In fact, my strongest creative ideas have come when I least expect them - when I'm driving or brushing my teeth, etc. NOT when I'm sitting at the computer, willing the ideas to come forth.
How about y'all? Do you find this to be true, as well?