asterisk users - Jan 2006 - chan ooh323 choppy sound

I terminate some calls on a h323 device (a quescom gsmgateway) from 
asterisk 1.2.3 with ooh323,
the customer is complayining about choppy sound on most of the calls, 
the only warning message I can see is :

src/chan_h323.c:944 ooh323_indicate: Don't know how to indicate 
condition -1 on ooh323c_102

(the calls sounds perfectly with iax/zap termination and the quescom 
seems to work fine with other h323 devices like cisco iad 2400)