I'm not really close to Stockholm but I guess I could send you a drive to try with if a better solution doesn't pop up - if I have one that matches. What type of motor are you driving? PMDC, Brushless AC etc? What voltage and current?
Things to check, in case you haven't already:
Is the polarity of the step- & direction signals correct (ie. active low/high) and is the wiring done accordingly?
Do you have enough current to drive the opto-isolators in the drive (if opto-isolated).
Is the pulsewidth long enough?
Are you losing on all axies or just one?