My system had what appeared to me to be a weird crash, but really I probably just can't see the simple answer. Hence all you experts out there.

System:
Computer:xeon CPU, quadro GPU, ECC ram, this is a dedicated offline CAD/CAM machine with no antivirus running
PMDX 126 with PMDX107
Smoothstepper ESS
4 leadshine closed loop ES-DH1208
watercooled 4KW spindle

Using Solidworks and Solidcam post-processed with FANUCmach

I had a 14MB gcode file running and about 1/3 of the way it decided to cut through the aluminum block like butter and skip to M30.

Prior to running any code I always restart Mach4 and every program starts with
%
O5000 (BSTEP14MMBULL.5R12X12IX12368.TAP)
(SUBROUTINES: O2 .. )        
G90 G17
G80 G49 G40
G54
M98 P9011
M01
N1 M6 T1
( TOOL -1- ROUGH DIA 4.0 MM )
G90 G00 G40 G54
G43 H1 D31 G0 X229.176 Y91.066 Z70. S10000 M3
M8

I normally dry run the program with the pmdx off to double check for ghosts. If all is clear I restart and re-run with a live system. This time it did something I am not used to. I did a dry re-run the program after the crash with the pmdx off and no issues. No idea where in the gcode this happened. The only difference bettween the dry and "real" run is pmdx was off and therefore the spindle, drivers, and steppers were off too.  My system is pretty well shielded. It runs off 220v but I have a line filter at the source. All cables are shielded with grounding loops minimized. I bet I could find a few spots to fix but overall I would say it is sufficient. Beyond random line interference from EM the only other difference from this run compared to others would be that this was a 14MB file and most of my runs are 8MB or less.

Any ideas?