Thanks, but I got the same behavior whether using cn=config as the directory name or slapd.d. If the directory doesn't exist I get the "invalid config directory" error and if it does exist I get the "Available database(s) do not allow slapadd" error.
If you're adding the config db, see the "-n" option to slapadd. I.e., your command should be .../slapadd -F /path -n 0 -l /path/to/file.ldif --Quanah -- Quanah Gibson-Mount