Hey Dean,
I'm going to speak to our HD/HDS expert here about this as I haven't come across that specific error but I have some basic troubleshooting questions;
Have you tried restarting the controller and PC and starting your job again, setting it up as you had yesterday, or have you only tried to operate it in its current state?
When you say the head has moved, along what axis and how far? Was the machine shut down overnight or left running? Basically, would you assume that the movement was don't via jogging/software control or by someone bumping into/pushing the gantry manually.
Thanks,
Chris@Techno
Christopher @Techno Inc. CNC Router Systems
Tech Services Department (http://technorouters.com/help TechnoWiki)