asterisk users - Dec 2007 - SIP hangup on call proceeding message

Has anyone experienced the situation where you receive a
PRI_EVENT_PROGRESS message from a PRI that is then sent to a SIP channel
where the SIP client (tried 2 different phones/manufactures) never
acknowledges, Asterisk resends the message two more time and then begins
hanging the call up?  
 
This is happening to me when my long distance carrier turns on account
codes (you make a long distance call that is routed to the carrier, they
send the caller a tone, then the caller enters in an account code for
billing purpose).  The call will connect, you can talk to the called
party for 20 seconds and then the call drops.
 
Thanks for any help.
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