If you are using the Edirol Midi Interface between the Computer and the Ketron then there is one LED light on the Interface which continually flickers to indicate a live connection to the computer and, when Midi is being played, a second LED flashes to indicate data transfer. You need to select the Edirol Driver in the MIDI Driver Panel. When up and working, I have found the Ketron SD2 to be be extremely reliable.

Lyn