Claus,
Did you manage to get your voltmeter checks done ??
Check the direction pins from your computer, as Hood said, you should get approx 5 Volts when jogging in one direction and approx 0 Volts when jogging in the opposite direction.
If you only get a maximum of 3.3 Volts then your existing combination of computer / controller is unlikely to work as is. Some options are to fit a PCI parallel port to the computer which has 5 Volt outputs or try another computer, get an improved quality controller such as the Gecko 540 or possibly use an external, USB operated, motion controller such as the Smooth Stepper.
Hope this helps.
Tweakie.