I recently came across someone with a MacBook Pro 2006-2008 model with the same issue.
Turned out to be the magnetic mechanism in the top case. You may need to replace the top case inclusive of the keyboard. They tested this by removing the top cover and powering on the laptop. 17" PowerBook is one of the easiest covers to remove. You may wish to plug a USB mouse to help you close the machine down after testing, should you decided to test.
Best of luck
Hi BGreg, it is going to sleep, not shutting down. It's running off my Leopard install disk so no personal settings are involved.
Hi Knucklesmac, I'll look into that magnetic possibility.
Maybe a heat issue, fans ?
Shutting down could also be a symptom of overheating. Consider getting something to help you monitor internal temps. I like this one:
because you don't have to invoke Dashboard to view the temps. They are visible in the menubar while you work.PowerBook G4 1Ghz 17", Mac OS X (10.4.11)
Hi Allan, thanks for replying. My PowerBook is going to sleep NOT shutting down if that makes a difference. The monitor program you mentioned sounds good but until I get this sleep issue dealt with I can not install it. Upon start up, it goes to sleep before I can even sign in to a user account. I ran the hardware test off my OS DVD and all passed.