NFS incompatible with Solaris jumpstart

Hi,

I want to jumpstart-install (initial installation of the Solaris operating system) a sparc machine from a linux server with kernel 2.6.8.1.

It works when using the nfs-user-server, but the sparc hangs after printing the OS prompt when using the nfs-kernel-server.

Any idea in how the nfs-user-server and the nfs-kernel-server differ and how to fix it?

regards
Hadmut