I have been using this dyno since the RSR days without a problem and regularly test down to 7 turn using a car battery topped up after each run.
I never hook a motor up without having the power supply and battery hooked up and on. Also ensure the computer and power supply is on a different electrical circuits, seems to cause problems or a electrical loop between the computer and dyno.
I wonder if line power quality might spike the dyno?
I have had the dos verison drop out, but not the Win version.