OK. I have a PPC g5 Dual 1.8ghz running 10.4.11...I was mixing an audio project the other night and right in the middle of my audio playing my mac just shut off!!No warnings, kernal panics, spinning ball or anything.I go to start it back up and I get the "power on sound" and it gets to the white screen right before "enter password" prompt and it just shuts off!! I was able to get it to boot using "comm + opt + o + f" and giving the command "mac-boot" but it will not start on it's own... After I finally get it to boot up, if I try to connect anything besides the keyboard, monitor, and internet, it turns off again! I was told to do a "nvram reset" but no results. I tried a "SMU" and a "PMU reset" and nothing same results- it wont boot unless I manually do so. I'm worried . Can anyone shed some light on the subject???