I was running v..020 for some time and now it does what you are describing. I start the computer and it runs ok, I start mach3 and it runs ok, I try to load gcode and it locks up. For me, I believe, it's a processor / motherboard problem. My computer is old. On the new one, for me to run the driver test, I had to right click on the tester and run as administrator once, after that it ran fine. Now the the issue for me is mach is not seeing the parallel port.