USB device shorting out PC

This is concerning a PC I assembled myself from all brand-name components considered at least better than average quality. For the most part, it works great... except when inserting a USB device it will often short out and reboot immediately.

Additional info:

- The electrical cord to the power supply is the typical 3-prong cord, and the wall socket's ground has been tested OK with a device like this
- it never shorts when inserting a USB device directly in the back of the computer (motherboard back plate/panel or whatever it's called)
- it only shorts when inserting a USB device directly into the top/front panel of the PC (which also include sound in/out connection)
- More than a single USB device can trigger the short (which should rule out a single memory stick's fault)

While it could be a power supply issue, I doubt inserting a USB memory stick would create such a spike in power than it would cause the PC to reset. I'm leaning toward a shorting / grounding issue with a connection of the front panel to the motherboard.

Does anyone have any other suggestion as to what might be causing the shorts?
Does anyone have any idea how to isolate the component at fault?

Any help would be greatly appreciated. Thanks in advance!