Copy + Paste not working for movieclip

Hi im makin an arkanoid game where you have to destroy bricks with a ball. I tested the game with a single brick on the screen, and it works fine (the brick gets destroed when the ball hits and adds to the score as well).

But as soon as i try to multiply the movie clip to have lots of bricks on the screen, the ball does not recognize the movie clip and goes straight through it.

Further more, after hitting a particular brick, they all disappear at once!

PLz tell me the prob! this assignments due on friday !