NTP Problem with Firewall Script

Need some help if you could please. Using Breezy 5.10, my iptables firewall script doesn't let me pass NTP stuff except by command-line /usr/sbin/ntpdate. I know that all NTP needs is 123 UDP, but for some reason the gnome date/time applet in the GUI won't let me click "Synchronize" unless I drop my firewall. Can you identify for me what might be the cause? Here's my current /etc/firewall.sh script:

iptables -F
iptables -A INPUT -i lo -j ACCEPT
iptables -A INPUT -p tcp -m tcp --dport 80 --syn -j ACCEPT
iptables -A INPUT -p tcp -m tcp --dport 443 --syn -j ACCEPT
iptables -A INPUT -p udp -m udp --dport 80 -j ACCEPT
iptables -A INPUT -p udp -m udp --dport 443 -j ACCEPT
iptables -A INPUT -p udp -m udp --dport 123 -j ACCEPT
iptables -A INPUT -p tcp -m tcp --dport 8888 --syn -j ACCEPT
iptables -A INPUT -p udp -m udp --dport 8888 -j ACCEPT
iptables -A INPUT -p tcp -m tcp --dport 500 --syn -j ACCEPT
iptables -A INPUT -p udp -m udp --dport 500 -j ACCEPT
iptables -A INPUT -p udp -m udp -s MYDNS1 --sport 53 -d 0/0 -j ACCEPT
iptables -A INPUT -p udp -m udp -s MYDNS2 --sport 53 -d 0/0 -j ACCEPT
iptables -A INPUT -p tcp -m tcp --syn -j REJECT
iptables -A INPUT -p udp -m udp -j REJECT
iptables -L

This permits for me:

* VPN
* Proxy hosting for my family
* DNS lookup
* web hosting (for when I test with family PCs against my Linux PC)

But it *does* allow me to lookup NTP from command line with:

/usr/sbin/ntpdate -b -s pool.ntp.org

But from the GUI in GNOME's date/time control panel, Sychronize button, it doesn't let me through unless I drop the firewall!
](*,)