I installed my Time Capsule to back up my iMac and my MacBook Air. It was working 100%. Suddenly, everytime I try to back up the iMac, a black curtain comes down the screen and asks ne in 4 languages to restart the computer. Now, it repeats the curtain everytime I try to instal software. It should be said that I have reinstalled Leopard many times without any result on the black curtain. After 4 reinstallments of Leopard, it does not recognize the password (aussie helped me). What should I do?