I actually got interested in the problem, and tried to recreate your code, even though you practically gave it to me. Had to sleep though :) I'll finish when I get home.
Anyway, as long as the physics time engine is based on your fps, any point when the window is moved will cause a drop in the fps. I recommend timing the loop and getting an average speed going. Then, pause the simulation if the loop time is longer than that. That way, when you release-click, the ball will move from where it started. You could just forget timing and estimate, which I don't recommend if you want accuracy. Ian
