asterisk users - Nov 2003 - NOTICE[16401]: File rtp.c, Line 417 (ast_rtp_read): Unknown RTP codec 72 received

the above-message keep popping up every second during a conversation 
between a
zap(fxs) channel and sip channel.

* eventually hung after a long while

we can talk to each other and we can ring one another without any problem.

i've had x-lite and x-pro register with * without this problem.

furthermore, i have ask my friend to turn off all codec expect 
g.711MLAW; that did not help
i then ask him to restart x-lite; some thing.
i then ask him to restart his pc; again the same thing.

i then restarted *; no help
i restarted the linux server; no help

i then changed the sip.conf with the following;

disallow=G729            ; Disallow all codecs
allow=ulaw                  ; Allow codecs in order of preference
allow=gsm

restart *; did not help
restart the server; again, did not help

i would not be so concern about this if it wasn't for the fact that this 
eventually killed *
i think this is also sucking up bandwidth as i can hear some jitters as 
we talk which never
happened before.

gratefully your,
patrick