forwarding iptable packets

["Jon Miller" <jlmiller@mmtnetworks.com.au>]

I'm having a major problem trying to forward packets from either a workstation of the LAn to the Internet.
I want to be sure I'm doing this correctly.

I set a forward rule:
$IPT -A FORWARD -i $INT_IFACE -o eth1 -p tcp --dport 1262 -j ACCEPT

Then I set a PREROUTING rule 
$IPT -A PREROUTING -i $EXT_IFACE -p tcp --dport 1262 -j DNAT --to-destination 192.168.xxx.xxx

All I can see using tethereal on the network is SYN packets.

Any idea what I'm doing wrong?

Thanks