Does this happen with any USB device you plug in?
If so,try grounding yourself before plugging in the device to eliminate the possibility of electrostatic discharge.
Though given the suggestion was to ground himself before plugging in USB ports to see if it stopped the bluescreens when sai USB was plugged in, having the PC turned off wouldn't really help here *
*yes, I'm just being picky here, its freezing here at work, so I need something to stop me thinking about it