iptables difference between FC3 and FC4

this message may be a little hard to understand as my english is not
very elaborate.

my server currently have multiple IP running on a single interface..
eth0
eth0:1
eth0:2

the problem with this kind of setup is that the client get always reply
by the first IP..
I searched for a squid config to fix this but didn't find any so I
choose to use iptables rules to have all proxies replying by theire own
IP.

with FC3/Debian I had only to run this for each of my interface and
everything was going fine
iptables -t mangle -A output -m owner --uid-owner 1000 -j mark
--set-mark 900
iptables -t nat -A POSTROUTING -m mark --mark 900 -j snat --to-source
<my IP>

but when I try this same iptables command on a server runnign FC4 it
give me the errors below. It seem that things are different between FC3
and FC4.

I now have this error under FC4:
Try `iptables -h' or 'iptables --help' for more information.
iptables v1.3.0: Unknown arg `--to-source'
Try `iptables -h' or 'iptables --help' for more information.
iptables v1.3.0: Couldn't load target `mark'

I loaded every possible modules related to netfilter and iptables, I
cannot find the way to fix the problem

I know this is not the proper place to ask for help about squid but if
someone know a squid configuration directive that is fixing this
problem and allow me to not use iptables rules at all.. I would really
appreciate to know it.

However my first question is this one : Is there a major difference
between iptables/netfilter under fedora core 3 and fedora core 4...
or is there another way to do the same thing with another iptables
command..


Thank You