My guess is your not getting one of the two phases from the driver to the motor. If you have a multimeter and can read the manuals schematic. Measure the ohms for each of the motors windings at the driver. Maybe measure the X axis first to see a good reading. If the ohms are similar (they won't be exactally the same) try swapping the Y axis 'driver to motor' wires to the X axis. This will tell you if the driver failed.
Be sure to do this when the main switch off. And beware the large capacitor near the drives can hold a charge for some time.
Tormach PCNC1100, Mach 3 R3.043.037, MastercamX5 level 3.