Some problems with vsftp.

Hi, all.
I have some problems with vsftp.
When I install vsftp, and ftp 192.168.1.220 by a windows client, it says :
500 OOPS: could not bind listening IPv4 socket
Connection closed by remote host.

When I used ncftp 192.168.1.220, it returned the same message.

netstat -an

Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:14547 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:21 0.0.0.0:* LISTEN

when I kill process inetd, listen port 21 disappear, so port 21 is not using by other apps.

Thanks.