Help! I'm experiencing almost these same symptoms, but only AFTER moving my set up from the basement to the garage. It had been working perfectly before the move. Triple checked all the wiring. Good. System is an older XP desktop with onboard LPT which does show 5 volts output. Additional symptoms are... for example - press Z+ the stepper motor runs fine BUT only maybe up or maybe down. It changes whether it goes up or down with each button press. I'm completely flummoxed.