I am having the exact same problem -- running Producer X3b (which I otherwise think is fantastic) and program cannot complete connection to control surface ("Connecting...") when try to connect to MCU or Extender XT. I'm at the end of a big project and cannot do my final mixing. Running Windows 8 Pro 64-bit. Tried Support's recommendation to reset MIDI driver configuration and control surface settings, many times, to no avail. The devices are not talking to Sonar, nor vice versa, although each side of the attempted connection seems to be functioning OK -- just no communication between them. Any help would be GREATLY appreciated. Thank you.