Monoprice Maker Select Plus- Doozie of a problem

So I've had my Maker Select III3 Plus for about a year and it's been wonderful up until 2 weeks ago.
I've never heard of anything like this.
Whenever I connect the printer to the USB port, the hotend begins to heat up.
Now, the computer recognized the printer and I can control it completely except for the hotend temp...it tops out, shuts down for a second, then repeats.
S3D, nor any other host software is sending a command to do this, no command to set a hotend temp has any effect.
Even when no printer software host is running it does this.
But wait, it gets better.
This happens even when the computer is turned off.
There's more.
This happens even when the computer is unplugged.
This happens even when the USB header is disconnected and the PSU to the computer is disconnected.
Now,
It does NOT do this when I connect it to a netbook.
I thought it may be a ground issue, since the charger on the netbook and the computer and the printer are not on the same outlet.
But the outlets all check good with a GFI tester and switching which outlet plugs to which changes nothing.
So, since it does not do this with the netbook, and I can print from an SD card with no issues, I figure it's gotta be the computer.

The problem is, I really want to restore the ability to print and work via the USB on my primary computer.
I have not altered the firmware of the printer in any way, and no other peripheral on my computer is effected.
I have even replaced the motherboard on the printer with the otherwise correct wanhao motherboard...no solution.

Does someone, anyone, have any ideas or suggestions?