I have a Windows XP Pro box (new installation) with the 3CXPBX beta3 running. My phones are Cisco 7960s (Sip Firmware) and the 3CX SoftPhone. I can call the extensions and they ring, but no voice is being :?: transmitted. I keep reading about the RTP issue, but nowhere can I find how to fix it. What do I have to do to get it to work?