Hi more likely the problem scenario is as following.
You drive one of the GPIO high or low that cause to curent flow. Next you reboot PC and it temporarry halts current supply from USB port but board continues getting small current via GPIO. This small current is not enough for board to stay alive and it stucks. Next PC goes up, board is stuck and PC does not detect it.
We are using another USB dongle from same provider called SUB-20 (http://www.xdimax.com/sub20/sub20.html
) with 32 GPIO. I checked it in the same scenario and did not see any problem. As far as I understand this board has diods preventing such problem