I bought the 915MHz 3DR radios and I am having the same problem. The ground and air radios link together and I can run mission planner 1.0 with the the APM2 using the USB cable but when I disconnect the USB cable and connect the telemetry cable to the telemetry port and try to connect to the APM2 with the radio link through mission planner the countdown timer goes the whole way to o and times out with no heartbeat packet received. I have checked the serial port baud rate in APM2 and it matches the radios. Don't know what else to do. Have re-flashed both radio units and the settings match but no luck getting the telemetry info through the radios back to the PC. Everything works OK through the USB cable. I will have to send the radios and possibly the APM2 back to 3d robotics if I cannot resolve this issue. I am running windows 7 professional 64 bit software . Running the radios at 57k and APM2 serial baud rate at 57k.