Check to see that the "ip_masq_ftp" module is loaded. To do this, log into the MASQ server and run the command "/sbin/lsmod". If you don't see the "ip_masq_ftp" module loaded, make sure that you followed the BASIC /etc/rc.d/rc.firewall-* recommendations found in Section 3.4. If you are implementing your own ruleset, make sure you include most of the examples from the HOWTO or you will have many susequent problems.