asterisk users - Oct 2006 - Polycom IP500 Problems

Hi,
Im having problems getting a polycom IP500 phone to register.   Ive edited
the xml files and appropriate .cfg files and it shows up registered with no
ip address and if I go into the phones status menu and pick lines it says
its not registered. If I tell it to upload the log file it doesn't say
anything about why its not registering / what errors its getting.
Any advice is appreciated.
Thanks
--Don Wisdom