So are you hinting that it might be a problem with USB cable? I don't have a multimeter, but I'll get one. If there is a short, will changing the cable fix the problem? Newbie here.

Yes, he is saying that there could be a short in the cable, but it could also be on the HEX 16b board. Just wondering, does the problem also occur when your HEX 16b isn't plugged in to it's power supply?
I personally find it a little odd that a USB cable would be defective in such a way that it would cross 5v and ground. The PWR and GND wires are on opposite ends, but I suppose anything is possible.