I think I finally found a fix for the unstable USB mouse issue that prompted me to buy an entirely new computer last year out of frustration. My USB mice (all of them, regardless of the port it was connected to) would repeatedly stop working and I would get a Windows pop-up saying "USB device not recognized". In every USB root hub in the Device manager, there is a Power Management tab. One of my two root hubs was set to shut off to conserve power. Unchecking that box seems to work.
There's one other poor bastard at work that has been having the same problem with his Windows 7 laptop. I'll have to test this out on him to make sure it's a legit fix.
EDIT: I also had to delete/reinstall the drivers for the USB Root Hub.