I was helping another user get a Broadvoice trunk working and below is what we finally settled on. The major difference between these and the other Broadvoice settings in this section is that the incoming (USER) settings are not used (as is the case with most consumer VoIP providers, because they treat you as an extension rather than a peer) and therefore the context statement is moved to the peer settings. This should work with FreePBX 2.4 and above and Asterisk 1.4 and above.
OUTGOING SETTINGS
Trunk Name: Broadvoice
PEER Details:
disallow=all
allow=ulaw&alaw
context=from-trunk
dtmf=auto
dtmfmode=inband
fromdomain=sip.broadvoice.com
fromuser=xxxxxxxxxx (your 10 digit broadvoice number)
host=sip.broadvoice.com
insecure=port,invite
qualify=yes
secret=xxxxxxxxxx (this is NOT your login password)
type=peer
user=xxxxxxxxxx (your 10 digit broadvoice number)
username=xxxxxxxxxx (your 10 digit broadvoice number)
INCOMING SETTINGS NOT USED
Registration String: YOUR 10 DIGIT NUMBER:YOUR SIP PASSWORD@sip.broadvoice.com/YOUR 10 DIGIT NUMBER