asterisk users - Jun 2005 - Sipura 3k answers then immediate busy signal

I have a sipura 3000 that I am using just to send calls to my mac asterisk
server. When you call the phone it rings, answers, and then goes right to a
busy signal. Any ideas?
Thanks for your help!
Jane

At the console in verbose mode I get:

*CLI> DEBUG[8501248]: File chan_sip.c, Line 663 (create_addr): Setting NAT
on RTP to 0
DEBUG[8501248]: File chan_sip.c, Line 554 (__sip_ack): Stopping
retransmission on 
'63e5425660664f565ce2c88b2cdc4d51@ipaddressofasteriskserver' of Request
102:
Found

*CLI> DEBUG[8501248]: File chan_sip.c, Line 3898 (check_user): Setting NAT
on RTP to 0
DEBUG[8501248]: File chan_sip.c, Line 554 (__sip_ack): Stopping
retransmission on '9a4ae229-c06315ff@ipaddressofsipurabox' of Response
101:
Found
DEBUG[8501248]: File chan_sip.c, Line 3898 (check_user): Setting NAT on RTP
to 0
DEBUG[8501248]: File chan_sip.c, Line 4950 (handle_request): Check for res
for 400
DEBUG[8501248]: File chan_sip.c, Line 980 (find_user): Call from user
'400'
is 1 out of 0
DEBUG[8501248]: File chan_sip.c, Line 554 (__sip_ack): Stopping
retransmission on '9a4ae229-c06315ff@ipaddressofsipurabox' of Response
102:
Not Found
DEBUG[8501248]: File chan_sip.c, Line 663 (create_addr): Setting NAT on RTP
to 0
DEBUG[8501248]: File chan_sip.c, Line 554 (__sip_ack): Stopping
retransmission on 
'417f48ea0b8c1c3e1b92305e1aa57976@ipaddressofasteriskserver' of Request
102:
Found
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