Diamondcard and XLite

I just started an account with Diamondcard and am trying to test it out with an XLite softphone. I’ve used their SIP configuration for asterisk on their support link and used my * IP as the domain and outbound proxy (+ port number - so 192.168.x.x:5060). I use my account ID and PIN number in the user name and passwords respectively. If I use their domain in the XLite configuration (i.e. usgw.ast.diamondcard.us) I can connect to their server and use the softphone, but if I use my * server IP I can’t. I get a registration error - 404 - Not Found. I used ethereal to monitor the traffic and it shows my account ID and my * server’s IP, not Diamondcards (i.e. xxxxx@192.168.x.x) when trying to register. Here is my sip.conf and extension.conf:

; Diamondcard.us termination
[diamondcard]
type=peer
username=xxxxx
fromuser=xxxxx
secret=xxxxxxxxxxxx
host=usgw.ast.diamondcard.us
disallow=all
allow=gsm
allow=ilbc

In extension.conf

[Local]
include => diamondcardterm

; Diamondcard.us termination
[diamondcardterm]
exten => _011.,1,Dial(SIP/${EXTEN:3}@diamondcard)
exten => _011.,2,Congestion

Anyone ever set up a Daimondcard SIP account on your * box?