sip 500 internal server error...is this a nat issue

[supa]

iam using AAH, and I can't seem to register w/ broadvoice:

Code:


asterisk1*CLI> sip show registry
Host Username Refresh State
sip.broadvoice.com:5060 7169541991@s 120 Request Sent



I then decided to do a sip debug and I get

Code:

-- Got SIP response 500 "Internal Server Error" back from 147.135.20.128
Destroying call '78a1df8376af856b5be47d08526ba340@127.0.0.1'
REGISTER 12 headers, 0 lines
Reliably Transmitting (no NAT) to 147.135.20.128:5060:
REGISTER sip:sip.broadvoice.com SIP/2.0
Via: SIP/2.0/UDP 69.162.210.234:5060;branch=z9hG4bK2d58f86d;rport
From: <sip:7169541991@sip.boradvoice.com>;tag=as0bdc88 04
To: <sip:7169541991@sip.boradvoice.com>
Call-ID: 78a1df8376af856b5be47d08526ba340@127.0.0.1
CSeq: 171 REGISTER
User-Agent: Asterisk PBX
Max-Forwards: 70
Expires: 120


and this
Code:

---
asterisk1*CLI>
<-- SIP read from 147.135.20.128:5060:
SIP/2.0 100 Trying
Call-ID: 78a1df8376af856b5be47d08526ba340@127.0.0.1
CSeq: 193 REGISTER
From: <sip:7169541991@sip.boradvoice.com>;tag=as5ffc08 dd
To: <sip:7169541991@sip.boradvoice.com>
Via: SIP/2.0/UDP 69.162.210.234:5060;branch=z9hG4bK4d07dd3f
Content-Length: 0


is this a problem with natting?