OK, here's a wierd one: when I try to put my dual 500 powermac G$ into Firewire Target Disk Mode (by booting while holding down "T"), my computer, about 20 seconds into booting, shuts down! 
I've tried disabling all extra utilities I have running, and enabling sharing via FTP and Remote Apple Events, but I really have no clue now. Any suggestions?
Thanks GREATLY,
Nancy
Ehm? When you boot it up into TDM the computer shouldn't even begin to boot up! A Firewire logo should appear on the screen and that's it, so if that is not happening then TDM is not being initiated correctly.
TOM
Tom,
Thank ou for your comments!
Observing more carefully, I can tell you that the machine never lights up the screen, and the disk drive makes no sound indicating accesses. It just shuts down before ever doing anything, which makes it seem like some kind of configuration parameter is set incorrectly, or there is some hardware problem. I've even tried two different keyboards, with the same result.
Any further help would be GREATLY appreciated.
-Nancy
If i have another FW Device hooked up to my Pismo PB when I enter TDM it shuts down too. Make sure you don't have any other FW devices hooked up to it. email me at pledoux@gmail.com if you need a walkthrough or other help.
Ok.. You may have already figured this out, but I ran into the same problem today.
When I held down the "t" key, it would attempt to boot for about 15-20 seconds, and then shut off.
The problem was the hard drive - Even though it is the only drive in the machine, the pins were set to Slave - Once I moved the pins (directly on the hard drive) to Master, it booted right into Target Disk Mode.