asterisk users - Jan 2006 - 0h323 - one way audio

I am using 0h323 on Asterisk CVS HEAD 19/07/2005.  I am dialling a h323 
gatekeeper.  He can hear me, but I cannot hear him.

I have a suspicion that it could be the rtp traffic, since he said that 
they need rtp traffic from ports 4500 - 65000.   So in 0h323.conf i set 
updstart and udpend, and in rtp.conf i set the ports here.

a tcpdump confirms there is two way traffic.
unfortunately, a 0h323 debug does not show much:

   -- Executing Dial("IAX2/UUNET59arbinet@a.a.a.a:4569-2", 
"OH323/27126801429@b.b.b.b") in new stack
     -- H.323 call to 27126801429@b.b.b.b
     -- Called 27126801429@b.b.b.b
     -- OH323/27126801429@b.b.b.b-5716 is ringing
ECNLONDON2*CLI> oh323 debug toggle
Verbose debug info for OpenH323 channel driver turned on.
Channel OH323/27126801429@196.43.16.25-5716 (call 'ip$localhost/13673') 
TX byte count is 4000.
Channel OH323/27126801429@196.43.16.25-5716 (call 'ip$localhost/13673') 
RX byte count is 7000.
Channel OH323/27126801429@196.43.16.25-5716 (call 'ip$localhost/13673') 
TX byte count is 5000.
Channel OH323/27126801429@196.43.16.25-5716 (call 'ip$localhost/13673') 
RX byte count is 8000.
Channel OH323/27126801429@196.43.16.25-5716 (call 'ip$localhost/13673')

do have any ideas?

thanks,
yusuf