Problems for driving LUDL stage

[mugger]

I am trying to use the labview and drive the LUDL MAC 2000 microscopic stage. My code is enclosed. Now I set the everything right, so I can set the stage moving speed and distance. It actually moves. However, I can only move once. When I click the run button in labview again, the stage does not move. So I was quite confused. I had to turn off the controller and turned on again so as to make it move for another time. There must be somewhere wrong, please help me find out.

[Nathan-P]

It sounds like after sending the first set of serial commands, it is putting the device your controlling into an unknown state. Its possible the serial data being sent isn't in the format your expecting.  Have you verified that the serial output is correct?  I know that sometimes LabVIEW doesn't convert escape characters properly (\r).  (http://digital.ni.com/public.nsf/allkb/5A5A050A3019A573862575F30061D49B)

Does the device work as expected when using serial commands directly, like in hyperterminal?