For loop and sine making a box?

Seriously, I have no idea why it’s doing this. Maybe it’s just my comp, but I tested it on another computer, and it did the same thing. I’m trying to make a circle accurately collide with a box. I tested with just adding a number, and the circle part worked fine with that, except it was not hitting it all the time.

Here’s the FLA: http://www.mediafire.com/?22imw2ln3h1