So you have 2 PhonePower accounts? And you're using different SIP credentials for SP2 or is it a cloned line? The PP proxy server doesn't like something in your SP2 configuration.
First thing I would do is delete SP2 and remake it.
If that doesn't work, I would download Phonerlite to your computer and configure it the same way you are attempting to configure SP2. If you get the same error, look in the Phonerlite debug log for exactly when/where it is throwing the error message. It should give some indication what it doesn't like.
If no luck with that I would call PP support.