I had the same problem with incoming calls disconnecting and had to run the two systems separately until I read this thread. The firmware upgrade did the trick. Thank you everyone.

After a very long conversation with a "techie" at BT I was offered the port numbers to open. They work well (UDP) but the first port range quoted by BT, 32000 - 36000, is 4000 ports. My modem/router's (SAMR4114) virtual server will not handle more then 1000 ports and I had to reduce this entry to 32000 - 32600. Does anyone know what effect if any this will have? I did find that ports 2467, 2727, and 5060 got the line working on their own. Unless I'm missing something?