These planets orbiting at 4:2:1 raitios so that the inner planet orbits two times for each orbit of the middle planet, and the middle planet orbits two times for each orbit of the outer. The question is, how would their orbits get reshaped if the mddle planet is much more massive than the others? Farther down the page is a Flash-based animation of this.
A work-in-progress Flash-based animation of orbit resonance. These planets illustrate a mean motion resonance of 2:1. The inner planet orbits twice for every orbit of the middle planet. The middle planet orbits twice for every orbit of the outer. If you select the Auto button, each pass of the inner planet's closest encounter with the middle (let's call it Jupiter) will tug it's orbit, making it more elliptical. I don't know if the reshaping of the orbit would be as shown, so I have direction buttons that allow the influence to be in either direction. This is to illustrate the concept of orbital resonance and how it can modify orbits.
(Note: Select the Auto button to see the inner planet's orbit change; I will do the same for the outer planet, but I don't have it working yet).