ntp handling in 6.0

[Dave]

Hello,
    Has ntp handling changed in 6.0-RELEASE? I've been through the handbook 
and /etc/defaults/rc.conf but haven't found the answer to this. I've got a 
machine acting as an ntp server for a network. When i run ntpdate -b <IP> 
from another machine i get the error "No servers suitable for 
synchronization found". Ntpd from these other boxes shows the same. From the 
local ntp server to the ntp servers on the internet works fine.
The local ntp server's configuration is as follows:

/etc/rc.conf
ntpdate_enable="YES"
ntpdate_flags="-b servername"
ntpd_enable="YES"
ntpd_flags="-c /etc/ntp.conf -p /var/run/ntpd.pid"

ntp.conf
server servername prefer
server servername
servername
driftfile /etc/ntp.drift
restrict 192.168.9.0 mask 255.255.255.0 notrust nomodify notrap

and on client boxes:

/etc/rc.conf
ntpdate_enable="YES"
ntpdate_flags="-b local ntp server IP"
ntpd_enable="YES"
ntpd_flags="-c /etc/ntp.conf -p /var/run/ntpd.pid"

/etc/ntp.conf
server local-ntp-server-ip prefer
driftfile /etc/ntp.drift

    Thanks.
Dave.