Thanks, I have a partial success which involved two steps:
I said "partial" because now I have a phenomenon similar (not the same, but close to) to the one I have with the SNOMs: The TLS link is reseted after a while and then a new (additional) registration is done. I'll continue search it per the tips I got on the other topic.
 
                          Thanks! __Yehavi:
 
2010/1/4 Brian West <brian@freeswitch.org>
OK to properly use TLS you have to setup NAPTR and SRV records and the DNS domain has to match the cert.  Did you do that?

/b

On Jan 3, 2010, at 9:32 PM, Yehavi Bourvine wrote:

> I've built the slef-signed root certificate and server;s certificate per the TLS wiki, and installed the root certificate on the phone (both manually and via the config files). I did not enter the "== untrusted ==" instead of the cerificate (as the Polycom's wiki suggests) as the pone doesn't allow this. It accepted the certificate.
>
> I've tried this on 501 (running 3.1.3 which is the last supported version on it), and 550 & 650 running 3.2.2.
>
>                             Thans, __Yehavi: