I've been using Mach3 and ESS card for quite a while with no problems. Recently, I've been having some issues with the steppers making a weird noise, and missed steps and unpredictable movements. I ran a rather large 3D file this evening, and got through the rough cut. When I started to run the finish cut, it ran well for quite some time, then all of a sudden stepper motor noises and out of control movements. The head plunged into my work, and continued to move, even when I hit stop in Mach 3. I had to hit the estop switch to get the machine to stop moving. Any suggestions of why this is suddenly happening would be greatly appreciated.

Running a G540 board with the ethernet smoothstepper and Mach 3.

Thanks in advance.