Raymond,

On your server you will have to load the 'ip_conntrack_ftp' module as
root. Do that and see if it fixes your problem. If it does, you can have
it load automatically at startup by modifying a line in the
'/etc/sysconfig/iptables-config' file:

  IPTABLES_MODULES="ip_conntrack_ftp"

These instruction will work on Fedora Core linuxes, and probably
others...I think. Good luck!

Troy