[SR-Users] Unable to make calls after integration with Freeswitch

Hi there. I had a working Kamailio proxy working where i could call from one polycom test phone to another.  But then I tried to integrate freeswitch with it... (following the article found at:  http://kb.asipto.com/freeswitch:kamailio-3.1.x-freeswitch-1.0.6d-sbc as a baseline. ) Now when I dial a phone, it's just silent for a few seconds... after which i get a busy tone.  I did a tcpdump and have been reviewing the file in wireshark.  It looks like my two test phones are registered properly... but as you can see, the INVITE is not getting an OK back.  It just keeps on retrying the invite.  I'm not sure how to go about troubleshooting this.  Any suggestions on where to start would be appreciated.  In the meantime, I'm googling around to see if I can find anything that might help me figure this out.  thanks.