ipfw port forwarding don’t work on 10.6 like in 10.5

Hello, I have squid configured in a tranparent proxy and i would like to forward incoming traffic on port 80 to 127.0.0.1 port 3128... On leopard, i use: ipfw add 002000 fwd 127.0.0.1,3128 tcp from MYLOCALNET to any 80 but in snow leopard (10.6) it does not work... kernel.log says : ipfw: 150 Forward to 127.0.0.1:3128 TCP 192.168.0.59:50142 209.85.229.113:80 in via en1 but nothing... Please help.