I won't deny that VOIP in general is probably not for the faint of heart. I own the 110 and have my ATT land line attached and used daily for local [free] calls but use VOIP for all of my long distance calling. That said, did you use the portal to configure your device or do-it-yourself? Either way, if you are in the US you should be able to make it work. Until Obi releases new firmware, two settings may be critical. First-Make sure you are getting at least rudimentary DNS name resolution by checking the status screen. If it shows your unit is trying to register to "0.0.0.0", change DNS 1 in the Network screen to 216.254.95.2. Leave DNS 2 blank. Second, in the SIP screen, make sure X_ProxyServerRedundancy is not check marked. This is contrary to the Callcentric instructions but may be required until Obi makes their change(s). If you used the portal to set it up you will need to enter the expert mode to check these settings and make the changes. Make sure BOTH the "ObiTalk" AND "Default" boxes are not checked. Then UNcheck the redundancy line and save.
Not guaranteeing these two things will fix your issue but you should give it a try.