I can't stop for loop mc and I don't know why my mc always be at the top left corner.

[Mr Wabbit]

When using the attachMovie function you want to use removeMovieClip.

So.

me=_root.attachMovie("mcBall2","b"+cur,cur); //Your current attachment type

me=delete _root.attachMovie("mcBall2","b"+cur,cur); //Current remove code
me=mcBall2.removeMovieClip();

There is almost no reason to use the delete function in AS2.
One case you may wish to use it, is if you wanted to completely remove an handler on the MC ie. an onPress.
Though I could be wrong about that my knowledge of the delete function is minimal as I don't use it.

If all is fine, remark as resolved.