NFS problems, mac & linux

[ejbr@comcast.net]

After many attempts and much swearing, finally got an NFS server running 
on a Mac G4 Powerbook (not my machine & I don't know OSX from shinola), 
with /Volumes/Alien shared.  I run on this Linux box:
sudo mount 192.168.1.102:/Volumes/Alien /mnt/alien

"mount" shows OK:
    192.168.1.102:/Volumes/Alien on /mnt/alien type nfs 
(rw,addr=192.168.1.102)

Problem is, I can't access /mnt/alien - even as root::
    root:/mnt/alien # ls -al
ls: reading directory .: Input/output error

Then I notice
edj:/mnt$ lk
.  .  .  .
drwxr-xr-x   3 root cdrw 1024 Aug 21 17:59 alien
.  .  .  . 

If I umount, /mnt/alien is properly root:root.

Why's that changing to cdrw group upon mounting?  I'm assuming the problem 
is at this Linux end someplace.  Any advice, hints, pointers? 
Thanks.

-- 
Ed Jabbour