nfs headache: can't read superblock

[Jean Spirat]

Hi,

i am trying to make FAI work on my debian box but i fail at the 'mount 
root fs' part on NFS:

fai02:/# rpcinfo -p 192.168.1.72
  program no_version protocole  no_port
   100000    2   tcp    111  portmapper
   100000    2   udp    111  portmapper
   100003    2   udp   2049  nfs
   100003    2   tcp   2049  nfs
   100005    1   udp    942  mountd
   100005    2   udp    942  mountd
   100005    1   tcp    945  mountd
   100005    2   tcp    945  mountd
   100024    1   udp  48209  status
   100024    1   tcp  39959  status

fai02:/# mount -v -t nfs 192.168.1.72:/srv/fai/config /mnt/nfs/
mount: 192.168.1.72:/srv/fai/config: can't read superblock


 For me NFS seems to run ok but if i try to mount via nfs i got this 
strange error about superblock, any idea ?

regards,
Jean.