if you still have the drive you took out, i would put it back in and then reboot.I have a G5 dual 2.0 running 10.5.8 that has been running almost continuously for the past 7 years. This weekend I was swapping drives - not the boot drive, the second one. I left the machine powered off overnight and when I tried to boot the next day, I get the white screen with apple logo and the spinner, and after 5-10 minutes the fans go turbo.
I was able to boot from the optical drive and run drive diagnostics and repair (from the original install disk), and here's what I got from the repair step:
Thousands of the same message:
>>Reserved fields in the catalog record have incorrect data
It still won't boot from the drive.
I've done a few other things like removed the battery - it tested at full strength. Booted while holding OF keys, reset nvram.
Pressed the internal reset button (pmu, smu?).
Unplugged it for an hour.
None of this resolved anything, same symptoms. so I reran the disk repair and got this message:
>>Checking extended attributes file
>>Keys out of order
I did this a few times, same messages.
At this point I think my drive is the problem, so I ran the installer, and it gives me the option to save the old system files and install the OS again. Will this kill my other files on that drive, or should I just get a new drive, install on that one, and attempt to recover my old files and configs?
i know that sounds silly, but i had the same sort of thing happen to my 06 mac pro. it was like the machine wouldn't play nice unless the hard drive buddies were both there. i don't know what the technical issue was, but after i put the removed drive back in, the pro was smiling back at me.
if you have another mac and an external hard drive, if the above doesn't work, i would remove the main drive, put it in the external and see if it's recognized by another mac. just to see if you get the same errors.
hope that helps.