scromwell-
Did you try putting tabs in first, then start water, then add clothes once a few inches of water is in washer? This will give them a head start in dissolving. Also maybe you are overloading the washer a bit so the clothes and tabs can't move around freely (DH is notorious for this, he can never figure out why his clothes aren't clean). Anyway, that's how I do it without a problem. Hope this helps.