Okay,

I made sure I had the same parameters in my configuration (commented out the ones that I had extra).

The following is visible in the Asterisk cli when the call from the other SIP phone comes in to the N900 (3450)

-- Called 3450
-- SIP/3450-00462198 is ringing
-- Got SIP response 500 "Internal Server Error" back from 192.168.2.94
-- SIP/3450-00462198 is circuit-busy
== Everyone is busy/congested at this time (1:0/1/0)


I still get the "Internal Server Error". I can't help to thing that it could be a SIP option in the general section that is messing it up (something that sip-sofia doesn't understand). What does your general section look like?

Also, what version of Asterisk are you running?

Cheers,

// Jonas