I found out what the problem was.
It appears to be a bug in the Polycom 430 firmware.
I have 2 lines on the phone and both of them use the same auth id but with
different servers.
It seems that if you make an outgoing call from the phone on line 2 and then
called party hangs up. Asterisk says
Hi,
I have a really strange problem with a Polycom 430 phone and Asterisk
1.4.20.
Currently If I dial the Polycom from my mobile phone answer the call on the
Polycom and then hangup the mobile the call ends fine on the Polycom.
But if I call from the Polycom to my mobile and then I hang up the
