SCSI disk corruption

OK, so I've been trying to install the Sept 24, 2003 snapshot on my 
non-Turbo mono cube.

I disklabeled it, got the bootloader installed (using Christian 
Limpach's installboot.sh script), newfs'ed the partition, and copied 
the GENERIC kernel over.

That boots.

The problem comes when I try to unextract the distribution sets.  I 
ftp'ed them over to the hard drive.  Almost always (but not every time) 
gzip -vt or tar -xzf fail blaming corruption of the file.  But I know 
they're stored correctly on disk, since sometimes succeed.

pid 586 (gzip), uid 0: exited on signal 11 (core not dumped, err = 27)

What's odd is that gzip and tar have no problems if the .tgz files are 
located on an NFS mount.  Also, cksum always returns the same value for 
the .tgz files.

The other thing is that when I shut the system down, it always hangs 
(or panics) when trying to unmount the root filesystem:
syncinc disks... Done
unmounting / (/dev/sd1a)...

Any suggestions?

TIA,
   -- MW