求助：我的proftpd不能连接

lithink

请各位DX帮帮忙，我的ftp连不上，报错如下：
421 Service not available, remote server has closed connection。

我在网上搜了很多贴子，还是没有解决。环境是：Solaris 8 for SPARC, proftpd 1.2.10, mysql 3.23.53, php 5.0.2。其中，proftpd.conf的配置如下：
ServerName "my ftp server"
ServerType standalone
DefaultServer on

Port 21
Umask 022

<Global>;
SQLConnectInfo ftpuser@localhost:3306 ftpuser
SQLAuthtypes Backend Plaintext
SQLUserInfo users userid password uid gid NULL NULL
SQLDefaultHomedir "/tmp"
RequireValidShell off
SQLGroupInfo groups groupname gid members
SQLAuthenticate users groups usersetfast groupserfast
</Global>;

MaxInstances 30

User nobody
Group nobody

<Directory />;
AllowOverwirte on
</Direcrtory>;

在系统中建有nobody，ftpuser的用户和组，/etc/init.d/proftpd文件的内容如下:
FTPD_BIN=/sur/local/proftpd/sbin/proftpd
FTPD_CONF=/usr/local/proftpd/etc/proftpd.conf
PIDFILE=/usr/local/proftpd/var/proftpd.pid

if [ -f $PIDFILE ]; then
   pid='cat $PIDFILE'
fi

if [! -x $FTPD_BIN ]; then
   echo "$0: $FTPD_BIN: cannot execute"
   exit 1
fi

case $1 in
   start)
   if [ -n "$pid" ]; then
      echo "$0: proftpd [PID $pid] already running"
      exit
   fi

   if [ -r $FTP_CONF ]; then
      echo "Starting proftpd..."
      $FTP_BIN -c $FTPD_CONF
   else
      echo "$0: cannot start proftpd -- $FTPD_CONF missing"
   fi
   ;;

   stop)
   if [ -n "$pid" ]; then
      echo "Stopping proftpd..."
      kill -TERM $pid
   else
      echo "$0: proftpd not running"
      exit 1
   fi
   ;;

   restart)
   ....
   ;;

esac

exit 0