Have you double check the integrity of the wiring and connections between the controller board and the steppers?
Have you checked the voltages that the parallel port is putting out, both with load and no load?
Have you checked the voltages that the controller board is putting out, both with load and no load?
Have you switched the stepper motors?
Have you done a search for "stepper emits a high pitch whine" and "stepper stalls"?
Also, maybe the stepper motor thinks you are overworking it and the high pitched whine is its trying to communicate that to you.
I am having trouble setting up MACH3 and have had really great help from folks here on CNC Zone, though to no avail. I am beginning to suspect that my wife has cast a spell on my new CNC because I am not paying sufficient attention to the Honey Do list.