Re: A clockwork solar system?
I did a computer simulation, once upon a time, to demonstrate the importance of resonances in determining orbits. It doesn't take long (in astronomical terms) for low-integer resonance ratios of, say, 2:1 or 5:2 to go away--the orbits of the bodies involved get rather strongly perturbed such that they settle into less resonant orbits (or depart the system entirely). But strong perturbations like this still occur even with ratios of, like, 12:37, if you wait long enough.
Anyway... the reason I would argue against the possibility of a clockwork solar system is materials. I don't know what you could make the gears out of, at that scale, and still expect it to run for billions of years. Especially if you expect the mechanism to have negligible gravitational effects on the planets themselves.
edit: Having reread the original post, I guess gears are not really under discussion. Still, tidal influences would likely prevent the axial rotation of the planet from remaining at precisely 360/circumnavigation. OTOH, I note that at least one moon in our own system rotates exactly once per orbit, so it may not actually be impossible. And if the "ancient" race is ancient on a scale of thousands of years, as opposed to millions, then perhaps the system would not have had enough time to devolve out of its original orderly motion. Especially if certain alien artifacts are still operating....