FTP/firewall problem

Hi all, this must have something to do with my firewall setup: ftp-ing gives me "illegal port command, 500" Although ftp-ing from for instance MC or console seems to work fine. I have a gateway machine, 2 nics, 1 connected to a adsl modem, other to hub, running a firewall script. what would be the setting to change? thanks. Jeroen Verstegen www.jota.nl