Stepper failure vs latency?

Recently, as I was making a rapid move (Y axis), I hear the stepper motor buzzing normally, when suddenly the buzz turned into a zing and the motor froze. Of course now I'm loosing steps. My solution was to slow that axis down, but then it happens again. The last time it did that, I checked it by moving 1 step at a time, and found that after 4 steps in one direction, on the next step it jumped back to the original position. Thinking that the motor failed, I connect a working axis cables from a working axis to the problem axis and found the problem followed the cable.
Eventually, the fix to that problem was to reboot the computer.

But still have the same intermittent problem.

If the latency requirements were violated in the setup, would that bring about this sort of malfunction? - That the computer would go into funk and straighten out upon reboot?

Motors are unipolar rated at 6 amps and 240 oz-in. Driver output is set for 5.5 amps.
Cables and connectors are fine. I failed to mention that I found one of the phases of the quadrature phase input coming into the motor driver from the parallel port had failed and rebooting the computer is what fixed it. The next time it happens that's what I'll try again. I'm wondering if exceeding latency limitations would cause the computer to go funky.

Just slowed the rapid moves to 40 ipm on X axis and 36 ipm onY axis on the Bridgeport mill. I also increased the base thread in the ini file from 50000 to 150000.
I'll see if the problem arises again with these settings.