Jeff;
Not sure about the E stop tripping. You may want to check the Mach3 forum, good help there. Machsupport Forum - Index
I just got an Ethernet smooth stepper working and I used a separate 5VDC power supply. I like the smooth stepper so far. It runs a Bridgeport retrofit and I think the machine actually runs better. Finally got away from Turbocnc (DOS) and floppy disks.
Jim