[FW] Firewire Drive Failing?

[Johns Lists]

I have a G4 MDD 1.25, with several internal and external drives.
In one of the drive cases (holds two drives) with the Oxford chip, I  
have one 80 GB and one 150.
The 150 does not show up anymore on the desktop, even though the 80  
does.
I ran Disk Utility, and during repair it shows all is well. It mounts  
in the window of D/U, but goes off again.
It shows healthy, but does not mount.
Now all of a sudden, it shows 0 files.
Drive tests well, all seems well.
I ran a defrag program on it (Genius) and it defraged the drive,  
showing lots of my files as far as blocks used.
Ideas how to get it to mount again?
Thanks,
John