Fedora Core 2. Port Forwarding Problems

["Василий Свиридов" <netspider@mail.ru>]

Hello all.

I had to upgrade my border machine because previous installation had 
failed for some reason. Any attempt to modprobe any netfilter related 
modules returned "Floating point exception"

I've installed fedora core 2 and tried to reuse my old settings i 
retained from redhat9 system.

Masqeurading works fine, but when i try to do port forwarding like this
iptables -t nat -A PREROUTING -p tcp -d <domainname.com> --dport 80 -j 
DNAT --to 192.168.20.40:80
rule adds itself fine, but port 80 is not accessible from outside.

when i try to connect from outside it doesn't say connection refused, it 
dies after a timeout.
/proc/net/ip_conntrack doesn't show any presence of connection, I tried 
to send it to -j LOG & ULOG but both end up empty.

I have to restore the firewall asap. Help me figure this one out. (I 
still have the option to rollback to rh9)

p.s.
sys.net.ipv4.ip_forwarding is 1