[CentOS] C6 gateway/firewall problem

Hi,

I'm using system-config-firewall (C6 x86_64, fully up to date) to
configure a gateway/firewall box. 2 nics, eth0 (configured as bridge0,
mtu 7200) connected to the lan, eth1 being connected directly to the
internet (public ip, mtu 1500). ssh port is open and accessible. nat is
working fine. I've put bridge0 as a trusted interface, eth1 is
masqueraded. I've put ports 20,21,80 as forwarded ports on eth1 to
lan machines.
Thing is nmap (and classical ways to access these protocols) say it's
closed.
I've tried to make 20,21,80 open and forwarded, to no avail.

Could someone give me a hand ?

Thanks,
Laurent.