nfsmount: need a server?

[Sig]

Using fai-cd, I can't boot and I get something strange in live.log:

Being: Trying nfsmount -o nolock -o ro "-ov2" 
<the-ip-address-of-my-server>:/srv/fai/nfsroot /live/image ...
nfsmount: need a server
nfsmount: need a server
nfsmount: need a server
nfsmount: need a server
nfsmount: need a server
nfsmount: need a server
nfsmount: need a server
nfsmount: need a server
nfsmount: need a server
nfsmount: need a server
nfsmount: need a server
nfsmount: need a server
nfsmount: need a server
nfsmount: need a server
nfsmount: need a server
nfsmount: need a server
nfsmount: need a server
nfsmount: need a server
nfsmount: need a server
nfsmount: need a server
Done.
Unable to find a live file system on the network

(with the real IP address of the server, of course)

What's strange is that the same nfsmount line succeeds at mounting the 
nfsroot when entered manually from the initramfs prompt !

The kernel line for getting this result is the following one:

kernel /boot/vmlinuz root=/dev/nfs 
nfsroot=<the-ip-address-of-my-server>:/srv/fai/nfsroot nfsopts="-ov2" 
FAI_FLAGS="verbose,createvt" FAI_ACTION=install 
ip=:<the-ip-address-of-my-server>:::::dhcp boot=live

The reason I use these options:
- ip=:<the-ip-address-of-my-server>:::::dhcp because I can't setup a PXE 
environment (my CD is meant to be used at home by DSL users who don't 
get a clue about things like DHCP and PXE while the install server is 
hosted somewhere in the wild)
- nfsopts="-ov2" because the install server uses nfs-user-server which 
is said to be incompatible (bugged?) with nfsmount default behaviour and 
the server can't use nfs-kernel-server because it is not a real server 
but a vserver

Hence my question: what is the magic kernel line I should use to 
successfully boot in such an environment?

Thanks in advance for your help!

-- Sig