Not sure if it is a Leopard problem, or just an OS X problem, but here goes. My wife called me to tell me the screen was locked up. She was using Safari. I told her to clock on the little blue Apple icon on the menu, and then was going to have her Force Quit. She tells me the Apple icon is BLACK, and nothing happens when she clicks on it. So I have her hold down the power button. Reboots, but now it is locked on the log-in screen. I can click on any user, but nothing happens. Sleep, Turn Off etc are also not responding. What do I do next? Any ideas? TIA!