samba - Oct 2002 - can connect when security = USER but not when security = SHARE

I have installed samba on freebsd-4.7. I have set up a share with "read
only"
and "guest ok" both set to "no". When I have
"security" set to user, I can
connect to the share, using:

mount_smbfs -I 10.11.0.25 //airyk@ARISTOTLE/new tmp/

but when i set "security" to share, i get an error message:

mount_smbfs: unable to open connection: syserr = Authentication error

and in the log file:

[2002/10/30 19:09:56, 2] lib/access.c:check_access(329)
  Allowed connection from  (10.10.0.220)
[2002/10/30 19:09:56, 1] smbd/password.c:pass_check_smb(552)
  Account for user 'nobody' was disabled.
[2002/10/30 19:09:56, 2] smbd/service.c:make_connection(331)
  Invalid username/password for new []
[2002/10/30 19:09:56, 2] smbd/server.c:exit_server(461)
  Closing connections


I don't understand why changing from share to user would make in not able to
connect, and I missing something?

erik