Very old thread but I'm updating as I had the exact same problem - except my callcentric line would fail to connect to any outgoing phone numbers called.
The instructions from RonR worked very nicely.

In addition, I had to go through all of the following areas and manually delete all previous changes and then check the ObiTALK Settings box:
Service Providers ->
ITSP Profile X General
ITSP Profile X RTP
ITSP Profile X SIP
Voice Services -> SPx Service
Please note that prior to having Callcentric I had a different service provider. I DID go through all of these areas and press the button at the bottom for "Revert All to ObiTALK Settings". After doing that for each area, I deleted the SPx profile and rebuilt it according to Callcentric directions.
However, the "Revert All to ObiTALK Settings" DIDN'T WORK. I still had a bunch of junk from a previous service provider that had to be manually cleared out.
Thanks,
Michael