Registration failed

when i try to connect to asterisk with x-lite i get the following error:
chan_sip.c:6037 handle_request: registration from ‘Zodiacal sip:1000@192.168.72.128’ failed for ‘192.168.72.1’

im using the asterisk live CD and following this guide: automated.it/asterisk/lah-3-6-05_1.html

i am following it exactly and have checked my user name and password a billion times. any ideas?