After a long run time, it seems that ZC (or more likely, Allegro) will cause some trackpad input devices to become intermittent. Plugging in a mouse, or using a secondary controller, such a a 'middle of the keys' joystick, will allow the user to close ZC, and then the trackpad device resumes. I've has this happen twice, with 2.50.1, both times, with Dell input devices.
I don't know if it would be possible to track down, much less solve this; but it's a good thing to know about, in the event that anyone with Dell hardware suddenly loses their ability to move a cursor/pointer.