Crimguy,
How about trying this with him before looking at a possible hardware issue? Your Dad is really saavy, and that always helps so much.
What is the approximate build date of his G5? *It's important to know this because it will determine the steps you may want to ask him to follow next.
G5s have several power management states and I believe this sounds like a full, extended sleep from which keyboard, LAN, mouse will not allow a wake. When in a full sleep mode, the power supply is one of the components that will suspend. I suggest you try a SMU reset as the next step since Apple hardware development notes show that SMU is the remaining means to wake a computer from full sleep mode.
If his G5 was born in late 2004, ask him to make certain the machine is completely powered down (by the power button) and then remove the power cable from the back and leave it out for, say, 15-20 seconds. Reverse your actions and try to power up, hit the keyboard, mouse, etc.
If his G5 was born in late 2005, make certain the computer is powered down, remove the AC power cable,the aluminum door, the plastics, the fan module. (I like to lay the machines on their side next for ease of board orientation.) Ask him to look for a small button on the system board and press it **1 time and only 1 time.** Make sure he goes only 1 time. It is about a 2-second press. He should then replace the AC power cable, making sure his power bar/surge protector is on, and then hit the power button and move the mouse or press a key.
With any luck, his G5 will stay powered on this time. You shouldn't need to, but you may want to check the system time afterwards.
This sort of thing is probably kind of distressing for your Dad, so I will check back in, ok?
CathyA
