Every time a usb device is connected or disconnected, the
circuit receives a voltage/current transient. An electrostatic
Discharge event is one such transient. USB is
susceptible to two main types of events: Overvoltage transients and Overcurrent events.
Whilst the circuits should be protected from the above one can only protect so far, you can easily get charged up to 15KV or so just walking across a nylon carpet. Moral is always earth yourself before you pick up the usb lead by touching bare metal on the case.
So either you have a dead part of the usb chip, just affecting that one port, or a bad soldered joint somewhere in the circuit (or both) you will have to live with it, if you are short of ports youcan always get an extender hub.