[@$3.1415rin]

you don't even need random numbers involved. When calculations are running at different fps on different machines, the rounding errors using floating point arithmetric will sum up and in special situations ( player hitting the edge of a crate, a barrel hitting an edge of a wall ) , you will get different results. I once wrote a little simulating program using simple strings and masses to simulate simple things, and it wasnt that easy to avoid oscillations and stuff due to this inaccuracy of the calculations. So I guess this might be a main reason.