The setup I currently have is a Aluminum enclosure for an Android Tablet. Inside the enclosure, a shielded USB cable is routed into the micro USB port and out through a small opening. This cable is then plugged into a 5V charging port on a power supply.
If I tie the enclosure to earth ground, have USB plugged in and shock the enclosure with a Piezoelectric igniter crystal (to emulate an ESD shock), it causes the tablet to reboot between every couple shocks. With USB disconnected, shocking the enclosure does not cause restarts. I've also tried placing a 1M ohm resistor between the enclosure and ground but that doesnt help either.
The one thing I also noticed after tearing the tablet apart is that DC ground is tied to chassis ground (shield) internally. Is there anything that can be done to help suppress the shocks and not affect the USB circuitry which is most likely causing the restarts?