This is not really nfs server related problem but a client problem. I upgraded a machine where only nfs client stuff was installed. It appears that the nfslock was not started in the boot (although nfslock script was found in /etc/rc.d/init.d - it was just not linked to the proper rc?.d directories). The nfs client needs nfslock started because clients need to run lockd too.
Oops... one thing missing: the upgrade was from 5.2 -> 6.1 after which the nfslock was not properly started
*** This bug has been marked as a duplicate of 6836 ***