vsftpd question: access error Login incorrect

[gameslover987-/E1597aS9LQAvxtiuMwx3w at public.gmane.org (Dave Peters)]

Hello all,

I have setup vsftpd on redhat 5 and have setup the following on /etc/passwd to lock the user directory.
vsftpd-2.0.5-12.el5 was installed on the server.

I created user and edit /etc/passwd
useradd -d /home/ftp/ftpuser/ -s /dev/null ftpuser > /dev/null 2>&1

edit /etc/passwd:
ftpuser:x:513:513::/home/ftp/./ftpuser/:/dev/null

vsftpd is running and listening on port 21. The iptables is allowing ftp.

I got user access error
Here is error from vsftpd.log
Thu Jan 29 20:45:44 2009 [pid 18752] [ftpuser] FAIL LOGIN: Client "10.0.2.123"

I am sure the username and password are corrected.
I have done on many server without this error.
Is there anyone can help?

Thanks in advance.

DP