error when adding new node...

Hi this error drives me crazy:

=ERROR REPORT==== 5-Sep-2005::18:50:02 ===
** System NOT running to use fully qualified hostnames **
** Hostname jabber-dev.autocom.pl is illegal **

i try to run cluster node on the same machine on what ejabber is already running i do it according to this guide:
http://ejabberd.jabberstudio.org/guide.html#htoc28 but when i make:
erl -sname ejabberd -mnesia extra_db_nodes "['default@jabber-dev.autocom.pl']" -s mnesia

i got error as abowe - this error is nonsense - besouse IT IS full domain name, so any ideas????

(i use "installer package")

thanks!