OSX 10.7.5 renaming attached Firewire drive

OSX 10.7.5 renaming attached Firewire drive

My Mini was running out of disk space, so I attached an external Firewire
drive and moved all the Home directories (a bunch of users on a home
machine) to it. I'm pretty sure that was done correctly, as it worked fine
for all accounts for about 9 months. Then, the OS started renaming the
volume on its own, usually adding " 1" to the volume name; thus, the OS
couldn't find any of the home directories on that Firewire drive upon
login, even though I could open the drive manually, and one would get a
generic startup desktop, because the volume names didn't match. I found
that, using an admin account with a home directory on the startup disk, I
could assign a fresh, new name to the Firewire drive, then get into each
user's advanced settings, and re-point the OS at the user's home directory
on the newly renamed attached drive. That would work for a couple of days,
until the OS again renamed the Firewire drive, and I'd have to repeat
those steps. Very annoying, and not something the other users, my family,
are about to do. So: why is the OS renaming that Firewire drive? Somewhat
contemporaneously, I've had about 3 hard crashes (grey text screen)
requiring a shutdown and startup. I've completely reinstalled the OS, BTW,
which did not stop the disk-renaming. Otherwise, I've seen no problems
with said Firewire drive; I have another external USB drive for backups,
and that doesn't have any problems of which I am aware.