My Photo Boot won't work. WHY?

We installed Leopard and since our Photo Booth hasn't been working. When I try to take a photo the light to my isight is green but there isn't any picture showing up on the photo booth. It will act like it is taking a picture (it counts down), but you can't see anything new appear. It also tends to freeze up a lot. I can see old pictures I've taken but when I click on them they don't show up. I tried shutting down the computer and then unplugging everything and restarting again but the problem still exists. Can anyone help?

Thanks!