Can't adduser using FreeBSD 7.0 (amd64)

[Froilan Romualdo]

Here's my uname -a:

FreeBSD fbsd.its1.localhost.com 7.0-RELEASE FreeBSD 7.0-RELEASE #0: Sun Feb
24 10:35:36 UTC 2008
root at driscoll.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC
amd64

Error upon running adduser:

pwd_mkdb: 14 uid is incorrect
pwd_mkdb: /etc/master.passwd: Inappropiate file type or format
pw: user 'froilanr' disappeared during update
adduser: ERROR: There was an error adding user (froilanr).

NOTE: I already read the FreeBSD handbook and google search the problem, but
I can't see a solution.

Thank you in advance.