Two things:
-Did you click "Apply" after configuring the port thingy? (doy)
-Did you know that OS X Panther has also a built-in firewall? By default it is not active but it might be worth to check it out. Launch that System Application and click the Sharing icon.

__________________
iMac G4 OSX 10.3.9
RAM 256MB
LW 4.10.5 Basic
ADSL anything from 3 to 8Mbps/around 1024kbps

"Raise your can of Beer on high
And seal your fate forever
Our best years have passed us by
The Golden Age Of Leather"
-Blue Öyster Cult-