This type of problem is usually a SCSI termination problem that originates
in the drive or the scanner. The problem could be with the hard drive, but
not with the PROM that needs replacing. (Note: This service program is for
replacement of a chip of the drive, not the drive itself.)
First try moving the terminator to another location. If the terminator is
on the end of your cable, move it to the scanner's empty SCSI port. If
it's on the empty port, move it to the end of the cable. If this doesn't
do anything, try removing the terminator completely.
Next, check the scanner to confirm that its internal terminators have been
removed. Finally, try using a different hard drive.