My RH9 ifup scripts:
/etc/sysconfig/network-scripts/ifup
/etc/sysconfig/network-scripts/ifup-post
/sbin/ifup
all mess with the iptables chain named "RH-Lokkit-0-50" whereas my "/etc/sysconfig/iptables" configures the chain named "RH-Lokkit-0-50-INPUT"

and I have the same problem:
"ifup eth1" =>
iptables: Table does not exist (do you need to insmod?)
iptables: No chain/target/match by that name

If I change all references of "RH-Lokkit-0-50-INPUT" in "/etc/sysconfig/iptables" to "RH-Lokkit-0-50"
and then "service restart iptables"

then "ifup eth1" works OK