Question : USB Shorting Out Motherboard

Problem: Rear USB Ports Shorting Out Motherboard

Approx 6 months ago I was called to a customers location to troubleshoot a computer that wouldn't boot.  Symptom: As soon as you push the power button you get beeps.  It doesn't even get to the point in the process where you can enter F10 to enter the bios setup.   After removing all the connected devices from the back of the computer, including an old LPT printer cable that was just dangling not connected to anything, I pulled the bios battery, plugged everything back in and the computer booted.  Done and Done!  Or so I thought!

Two weeks later the problem returned.  This time I suspected the problem was related to a USB cable problem.  I replaced the USB cable going to the new printer with a known good cable. The computer worked perfectly for 6 months.

Yesterday, the problem returned!  I removed the BIO's battery, plugged everything back in and got the same BIOS beep codes.  Brought the computer back to my office, connected to my setup (ps2 keyboard ps2 mouse, VGA (Monitor).....no USB devices plugged in at all) computer booted with the date and time error you get anytime you reset the motherboard.  I entered the BIO's set the date and time and rebooted to windows.  No Problem!  Shut the computer down (complete shutdown), and restarted 20 times prior to returning to their office to hook it up.

I get there, hook everything up (ps2 keyboard, USB mouse, USB printer).  BEEP BEEP BEEP!  UGH!  So I removed all the USB devices (except the  mouse) and the computer finally boots to windows.  Heres where it gets interesting.  I grab the USB printer cable and reach around back and plug it in.  When I return to the screen the computer is booting.  Apparently, plugging in the USB cable shorted the motherboard causing the shutdown and reboot.  The computer did manage to boot to Windows so both the USB Mouse and USB Printer are connected and working... ...at least for now.

QUESTION:
1.) what could be causing this to happen?  Obviously the rear USB ports are causing the motherboard to short-out randomly.  Is there anything that I should check before telling the customer that they need to replace the Motherboard or purchase a new computer?

2.) what could have caused this to happen in the first place? Simply plugging and unplugging USB devices shouldn't cause this.  I just ordered a CyberPower Battery Backup for the system.  The Client has had power issues in the past.  I'm thinking perhaps a power surge caused the problem to begin with.  Is this possible?

3.) Should I remove and re-seat all expansion cards and memory or would that be a waste of time?

Thanks

Answer : USB Shorting Out Motherboard

Possibly someone inserting a USB device the wrong way and using force has damaged the USB socket.  Or possibly leaning on the connection and bending the internal connectors.  Or trying to insert an incompatible plugin device (can't think of any at the moment).  Those are physical connection damages.  I've seen damaged USB sockets and they are not pretty.

If it is internal then the USB chip has gone.  Could be a power spike or a bad motherboard (faulty capacitors) or a faulty power supply.  

As for point 3.) that would be a waste of time.

You'll get some more comments from other experts on this.