I have a Mac Pro 8 core that is almost 2 years old. Still running Leopard and 10.6 I believe. This morning all worked great, and after a lunch break the 30" Apple monitor won't turn on. The power lights on the monitor. We substituted an older 22" we have and that won't work as well. We tried both video inputs on the back on the computer and still nothing. When we turn on the computer we hear the Apple signature sound and even though there is no visual on the monitor, this computer has a QuicKey keystroke to shut down the computer and this works. Any suggestions? Is this a graphics card failure? thank you.