Wow, I wish I could help you, I have been having the same problem with the plasma cutter on my cnc! I get random windows popping up on the computer and an instantaneous Estop when the torch lights. It has to be noise from the torch. I spoke to a Miller rep and he suggested contacting someone at Miller that may know what is causing this as it could be an internal problem in the plasma cutter. Strange because it worked perfectly fine for years then all of a sudden it won't work right anymore.
Anyway, good luck, I'm gonna follow this thread, interested to see what you find out.