Euro, If it is the code that changed it, it would probably be a G20 or a G21 but the ratio isn't 10-1. It will put your machine in Imperial or metric units. Go to MDI and typr in G 20 G 50 and hit enter. Now type G1 X1 F10. Does it travel 1 inch?
Micro steps are not set in Mach, they would be set on the drives. If you haven't changed anything mechanically, I doubt this is the case. Some drives change this option with dip switches, others with jumpers I think (possibly one fell off due to vibration?) and others aren't adjustable.
Brett