I would check the USB cable and USB port on the PC/HUB. I always try to trouble shoot the easiest most overlooked things first. I never ever assume someone has trouble shot the cable cause I use to tend to overlook them. The fact it worked fine for a month then suddenly out of the blue died has me thinking perhaps the cable was faulty or perhaps the port on the PC had issues. It also explain why the toolbox isn't seeing the board at all.
I tried a different cable that I have lying around and the toolbox is still saying "no device connected".
I then tried the original cable and plug it to an XD75. Cable is working fine as I'm using the XD75 to type this message.
Also, I just remembered another detail. Would a static shock destroy a keyboard?
Because just before I left the office for that weekend, I got a small static shock when trying to move my keyboard. I didn't think any of it at that time so I just left without typing anything to test if it was still working after that.