Ah ha - On a completey different system - Vaio Laptop, that worked fine with Pvt build 1013. Installed 1016, and now have same symptom - no audio heard. Go back to 1013, and it works again. I don't recall the exact compaq models (they're at work) but I'd bet now that that is not the problem. The operation here is that I am dialing into the "Voice Response System" on the Asterisk server with the default sample setup, so the server is generating the audio stream itself - it is not a client to client connection. The UDP ports are the standard (8000 for RTP, 5060 for SIP), no proxy, no NAT involvement (all done testing done in private address space, using "send internal IP"). I'm suspecting something in how Asterisk does the streaming or encoding on the protocols and you guys read it? All protocols tried - G711a, G711u, GSM - react the same way. Let me know if there is any way I can help if you want.