After further review (and after trying your suggestion) I have discovered it is only the iMac that can not access the G5. I also have a laptop (running OS 10.8.2) and it can access the computer via the finder. The iMac still can not.
One thing I did notice is that I can not turn off file sharing. Also, after a quick restart I can no longer share the screen either (from either computer).
It's getting weirder and weirder.
Whew, might try this on the G5...
Safe Boot , (holding Shift key down at bootup), use Disk Utility from there to Repair Permissions, move these files to the Desktop.
/Users/YourUserName/Library/Preferences/ByHost/com.apple.networkConnect.<12 digit number>.plist
(You'll need to Trash the originals of these following ones since move only copies them)
Looks like in 10.5.8 on my G5 that these files cover it...
Then reboot once more.
PS. Safe boot may stay on the gray radian for a long time, let it go, it's trying to repair the Hard Drive.
The G5 will not share it's screen so I have no way of doing this (that I know of). No minitor I have will hook up to this antique computer (I have an iMac and a laptop) and in the past I always just shared it's screen to do any maintenance to it.
Is there way to do all this without a keyboard, mouse and monitor?
BTW, after turning off remote share and turning on screen sharing on the iMac and laptop they are both talking again. I can now share files with the G5, but can not share it's screen.