[HELP] g.729 codec problem

the problem appears in local calls from SIP to SIP clients. For the firs two seconds the RTP pass through but after this time the stream is full of interrupts.
Everything works fine on outgoing and incoming calls with g729 codec over h.323.
When I listen voice mail there is not any kind of interrupts.

Any ideas what is wrong in my configuration???



port = 5060 ; Port to bind to (SIP is 5060)
bindaddr = ; Address to bind to (all addresses on machine)