Problem: I just unboxed a new computer monitor for one of our older MacPro machines (MacPro1,1). I cloned the harddrive using my existing classroom software set. When the computer would go to sleep, it would not wake up.
Solution: I first thought that maybe these new off-brand monitors were the problem. You get what you pay for, right. Then I thought that it might have something to do with the DVI connection. I tried VGA-> no change. The monitor would not wake up after the computer goes to sleep. Then I thought that the graphics card was freaking out. Fortunately for me, I have two identical systems to swap parts. No change. The computer with the sleep problem, still has a problem. At some point I hard reboot the computer and immediately click on the Sleep button on the log in box. Aha, I finally see the kernel panic screen. Now I ‘m thinking that it might be a software problem or a bad harddrive. I reboot with a system disc and run Disk Utility > First Aid. It finds a bunch of problems and fixes them (so it says). I reboot the machine and its still panicking when you hit the sleep button. So, I reboot again from the system disc and do a new install of the OS (10.6). Shazam that works. No more panics.
This article from Apple was helpful. ”You need to restart your computer” (kernel panic) message appears (Mac OS X v10.5, 10.6)” http://support.apple.com/kb/TS3742