drakI don't see how it can be anything but hardware if it's a randomly arising issue. If no changes occur, especially on the software end, then it has to be either the mice, the USB ports, or worst case scenario, the motherboard, correct?
Then, if it's the USB hubs or the motherboard, is there anything I can do besides getting a new motherboard?
Anything to look for on the USB ports or motherboard for indicative damage/problems?
mice: possible but that would be one awful coincidence.
USB ports: also another awful coincidence that all of them would be messing up at the same time. If your keyboard or other USB devices don't have any issues, then there's pretty much no chance it's your USB ports.
motherboard: that's what I'm thinking, which sucks.
I don't think there's really anything you can visually scope out to see if it's the motherboard. It could just be that it's crapping out on you. As previously mentioned, the polling rate was the only other thing to look out for, but if you've changed it all around with the same result, then it indeed might be the motherboard. How long have you had the motherboard for?