I had same problem, but found reason and solution.
Ubuntu NEED opened udp 111 port on server.
I have checked binds on server ( freebsd ) and found udp 11 port binded to localhost.
Just after that, I restarted rpcbind, mountd and nfsd services on my freebsd-server and all going ok :)
Thank's to wireshark - it's really helps discover problems :)
I had same problem, but found reason and solution.
Ubuntu NEED opened udp 111 port on server.
I have checked binds on server ( freebsd ) and found udp 11 port binded to localhost.
Just after that, I restarted rpcbind, mountd and nfsd services on my freebsd-server and all going ok :)
Thank's to wireshark - it's really helps discover problems :)