asterisk users - Dec 2004 - IAX2 calls failing one way.

Hi,
I'm having trouble getting IAX calls through in one direction. On the
receiving end I see:-

Rx-Frame Retry[ No] -- OSeqno: 000 ISeqno: 000 Type: IAX     Subclass: NEW
   Timestamp: 00014ms  SCall: 00001  DCall: 00000 [1.142.164.215:4569]
   VERSION         : 2
   CALLED NUMBER   : 2003
   CALLING NUMBER  : dave
   CALLING NAME    : Dave Smith
   LANGUAGE        : en
   CALLED CONTEXT  : from-dave
   USERNAME        : g6crv
   FORMAT          : 2
   CAPABILITY      : 65283
   ADSICPE         : 2
   DATE TIME       : 160927376

Dec 23 17:52:34 NOTICE[98310]: chan_iax2.c:5390 socket_read: Rejected
connect attempt from 1.142.164.215
Tx-Frame Retry[000] -- OSeqno: 000 ISeqno: 001 Type: IAX     Subclass: REJECT
   Timestamp: 00003ms  SCall: 00001  DCall: 00001 [1.142.164.215:4569]
   CAUSE           : No authority found

Rx-Frame Retry[ No] -- OSeqno: 001 ISeqno: 001 Type: IAX     Subclass: ACK
   Timestamp: 00003ms  SCall: 00001  DCall: 00001 [1.142.164.215:4569]

I have a context in extensions.conf called [from-dave]

Any clues as to why this is failing?
thanks
Mike