asterisk users - Jun 2011 - Immediate 180 Response on Invite

Hello,

When an INVITE packet is received, Asterisk immediately responds with
a 180 RINGING response before it receives a response from the
provider.  Furthermore, when this occurs, no ring tone is created on
the caller's end.

I've played around with the progressinband setting, but to no avail.

Any idea what is happening here and how to solve it?

Thanks,
Elliot