asterisk users - May 2004 - 403 Forbidden since upgrading

Hi,

I upgraded my local Asterisk (the last version was quite old), and since
then, whenever anyone tries to call me via SIP/IAX thru my external
Asterisk, they get "403 Forbidden" as soon as I pick up.

I have no trouble picking up when someone calls via PSTN.

Basically, my phone (Firefly softphone) will ring when they call, but will
disconnect as soon as I pick up.

It won't even go to voicemail, this is from the log on the localiax;

    -- Accepting unauthenticated call from X.X.X.X, requested format = 4, actual
format = 4
    -- Executing Ringing("IAX2[remoteiax@remoteiax]/16385",
"") in new stack
    -- Executing Dial("IAX2[remoteiax@remoteiax]/16385",
"IAX2/torh/2201|20|Ttm") in new stack
    -- Called torh/2201
May 18 18:02:32 WARNING[671760]: chan_iax2.c:2838 iax2_send: timestamp is 0?
May 18 18:02:32 WARNING[671760]: channel.c:1445 ast_prod: Prodding channel
'IAX2[remoteiax@remoteiax]/16385' failed
    -- Call accepted by 192.168.128.4 (format ULAW)
    -- Format for call is ULAW
    -- IAX2[torh]/6 is ringing
    -- Nobody picked up in 20000 ms
    -- Hungup 'IAX2[torh]/6'
    -- Executing Hangup("IAX2[remoteiax@remoteiax]/16385",
"") in new stack
  == Spawn extension (iax, h, 1) exited non-zero on
'IAX2[remoteiax@remoteiax]/16385'
    -- Hungup 'IAX2[remoteiax@blackfell]/16385'

Are there any obvious places I need to look? 

Tor