This might belong in the Leopard Tips sticky, but it's more to do with a rather long-term OS X problem solved by Leopard feature.
Now I know you wireheads probably have always been able to fix this via telnetting into the apparently locked-up Mac, kill a process or two, and away you go. But for those of us less technically inclined: Sometimes when a Mac comes out of sleep, or just coming out of screensaver or switched-off display mode, everything will come back up just fine, but the screensaver or switched-off display won't respond to a keyboard or mouse click. The Mac is alive and well, but you can't do anything with it because you can't see the desktop (sometimes hitting the power key on portables, and then the S to put it to sleep, and then wake it, will work, but sometimes inbuilt or external pointing or keyboard devices just flat aren't recognized.)
You're only choice, really, is to hold down the power button for 10 seconds to power down the Mac, and then start up again. I've never had this corrupt a hard disk or anything, but if you've had something going on in the background, like exporting an iMovie, or 3D rendering or a long back-up or copy, or whatever it is you do with your Mac that may have to run awhile -- even just unsaved documents -- you hope it's finished or saved, but you just can't be sure.
If you have another Mac available to screen share the unresponsive Mac, select the pseudo-frozen Mac from your other Leopard Mac, screen share, and the screensaver or switched-off display *will respond* to click or key press input from the remote Mac. Screensaver shuts off or display comes back to life, no problem, without risking a blind power off.
Now I know you wireheads probably have always been able to fix this via telnetting into the apparently locked-up Mac, kill a process or two, and away you go. But for those of us less technically inclined: Sometimes when a Mac comes out of sleep, or just coming out of screensaver or switched-off display mode, everything will come back up just fine, but the screensaver or switched-off display won't respond to a keyboard or mouse click. The Mac is alive and well, but you can't do anything with it because you can't see the desktop (sometimes hitting the power key on portables, and then the S to put it to sleep, and then wake it, will work, but sometimes inbuilt or external pointing or keyboard devices just flat aren't recognized.)
You're only choice, really, is to hold down the power button for 10 seconds to power down the Mac, and then start up again. I've never had this corrupt a hard disk or anything, but if you've had something going on in the background, like exporting an iMovie, or 3D rendering or a long back-up or copy, or whatever it is you do with your Mac that may have to run awhile -- even just unsaved documents -- you hope it's finished or saved, but you just can't be sure.
If you have another Mac available to screen share the unresponsive Mac, select the pseudo-frozen Mac from your other Leopard Mac, screen share, and the screensaver or switched-off display *will respond* to click or key press input from the remote Mac. Screensaver shuts off or display comes back to life, no problem, without risking a blind power off.