Hi Karl..

At last! Someone with the same problem.. I ran a piece of code last week with 16000 lines and it was not until near the end that it stalled my x axis.. The code was making a rapid move at 45 degrees for 11mm and then stalled the x axis.. I have now spoken to several people about this problem and between us have eliminated most of the potential problems.. What remains is;

Re-install Mach3 including driver..
Trying a different PC in case it is the parallel port..

I will dive into the workshop and try both these things and report back any success/failure..

Steve..