401 Unauthorized problems

Hi,

My sip.conf is found below. Both my Asterisk and my xlite client are behind NAT.
If I try to register to the hostname with the following config, I get a 401 Unauthorized. However, if I put in the public IP address, my xlite registers.
The only way to get my xlite register against the dyndns hostname is not to set a password.

Any help is greatly welcomed.

[general]

bindport=5060
bindaddr=0.0.0.0
localnet=192.168.1.0/255.255.255.0
externhost=xxx.dyndns.org
disallow=all
allow=ulaw
allow=alaw
allow=gsm
qualify=yes
language=fr
dtmfmode= auto
defaultexpiry = 1800
nat=yes

[2007]
type=friend
username=2007
secret=123456
host=dynamic
context=incoming
nat=yes
canreinvite=no

Post the SIP AND CLI DEBUG!!!