I have an old HP Compaq 6200 / i7 etc. The issue is I can't get anything to work consistently in the rear ports except an HP printer. I've tried multiple keyboards and mice, but they all stop working after a few minutes. Only the front USBs work properly.

So I replaced the motherboard with the identical one and, lo-and-behold! It's exactly the same. No working rear USB ports.

The box originally came with Win 10 on it, but I didn't notice anything till after I dumped Windows. I don't want to put Windows back on to test my silly question, so does anybody have any ideas on this?

OK, this is insane.
I've been looking for this solution for close to 6 months, and I finally replaced the MB, and it has the same issue. What the heck?
So more searching and I actually ended up finding something in the bottom of a thread on an Ubuntu forum. A 1-line command, instead of major scripting solutions.

I used it on this new MB, and it worked. Going to pull this board and put the original one back in tomorrow and check it out.
Will post results.

Here is the command:

(Thanks to "Dinesh" from May 2015)

Can you believe it? 6 months!!