waaaay simpler method to do this;
after parenting the ikSolver to the control for it, you can parent that control to the controller for the whole body. This means that if you move the body, all the controllers with it (so when the creature jumps, the legs go too....). So how do you get it to bob around with its legs held steady on the ground (or anywhere)? Simple - create a locator. Then, point constrain (preferably, although I suppose occasionally a parent constraint can be used) the ikSolver's control handle to the locator (they don't even have to be in the same loaction either, although for obvious reasons doing this makes sense.). This will keep the feet in one posistion, allowing the body to move around without disturbing them. And it even has a built-in switch - when you want the thing to jump from that spot, simply set that point contraint's attribute to '0', and away you go.