FreeBSD5.2.1 - adduser pw: user 'user' disappeared during update

Hello !

For the first time after installing FreeBSD 5.2.1, I am trying to add
a new user, but without success so far. I have tried many times (as
root), with /usr/sbin/adduser and also with /stand/sysinstall >
Configure > User Management > User (Add a new user to the system), but
the operation seems fo fail at the end, when I give the final YES. I
get the following error message:

pw: user 'user' disappeared during update

I have checked on the Web giving the error message as input to google,
but got only one highly pertinent message. In the end, the guy says he
re-installed FreeBSD, wihich I cannot do right now.

I checked with the command vipw, and emacs shows the lines
corresponding to the users I attempted to create along with the other
users I created at install time. There is no subdir under /home for my
attempts at creating those users,  nor can I log into the system with
those users.

Please, could someone help me with this message?

Salutations, Louis Harvey