EMC randomly shutting off (Toggle F2)

Did you by any chance change the computer cable or machine cable or the socket that they were plugged in ?
Might be there is no ground to the computer or machine so they are not on the same potential level.
Or there is something causing spikes on the parallel port inputs.

I tried putting the hard drive in a different computer, didn't fix the problem.
I opened up the box containing the breakout board, and Gecko drivers. Checked all connections. Found a loose "direction" connection on the Z axis. Didn't fix the problem.
I tried running the program without power to the steppers, and was able to run the full program.
All three axii are powered by individual power supplies, so I am in the process of seeing if I can isolate the problem to one drive.
With Z disconnected, X & Y powered the program stopped.
With Y disconnected, X & Z powered the program ran.
And as I am typing this, with X disconnected, Y & Z powered, the program stopped.
So, I think the problem is somewhere in the Y drive.
I'll try changing X and Y drivers/power supplies etc. and see if I can figure out what's wrong.
Thanks for the replies.
Rick

This is a completly different machine and software, but a strange problem with my 3D printer was caused by a broken stepper motor wire.
The printer would lose serial comms when the Y axis was in a particular place. It turned out that in this position a break in the X axis stepper wires was wobbled.

So, the problem might be in a different axis, but made evident at certain Y positions.

So, I've swapped combinations of drives/power supplies, and axii around and all fingers point toward a bad stepper drive. The problem follows the drive. I contacted Gecko and they agree that it sounds like a bad drive, but they have no idea what kind of problem would cause the software to shut off.

Is there any explanation that I could give them?

Thanks
Rick

Have you tried swapping stepper cables? (if any of them move during work)