I just installed LxAdmin on Centos 5.9 Final and the ftp was not working by default.
I got it working eventually and I share my experience for those who have the same problem.

1.) Firewall
Make sure the firewall has port 21 open.
Open the iptables file: /etc/sysconfig/iptables

You need to have this line in this file, if not include it

-A RH-Firewall-1-INPUT -m tcp -p tcp --dport 21 -j ACCEPT

2.) Enabling the ftp server
Strangely the ftp server has been disabled, so I had to enable it.
Go to /etc/xinetd.d/pureftp and open it.

disable = yes


disable = no

in this file then save it.

3.) Restart the services:

service iptables restart
service xinetd restart