heh, was the 5000 stone persona guy? I think it's the "I caught a fish thiiiiiis big" syndrome. ;)
If you had 7 flushes that produced stones, then you are due for 2 or even 3 flushes that do not. And that's okay. :) It jsut means you're moving the deeper stones to the fore, but the distance is too great to allow them to get ALL the way out, or they need to de-clump. Just keep up with the herbs and lecithin and flush again in 2 weeks.
the pattern I've noticed is 2 flushes w/o success followed by a fantastic flush that results in a huge stone. :)