My full settings (that work):

Window: Account Setup (don't put dashes in your phone number)
User Name: 174xxxxxxxx @ proxy01.sipphone.com
Password: gizmoprojectpassword

Advanced settings:
Connections Tab:
Transport: UDP
Port: 5060 (default)
all the others are defaults

Authentication Tab:
empty

STUN Tab:
STUN server: stun01.sipphone.com
STUN port: 3478

I use OpenDNS for name service.

I am behind a chain of THREE DLink routers.