I recently upgraded to Windows 8.1 from Windows 7 Home Premium. My USB ports will stop working until I unplug my Netgear N600 Wireless Network Adapter then plug it back in. For some reason it only happens when I download something. This never happened in Windows 7 but happens everytime I attempt to download something in Windows 8.1. My motherboard is an ASRock 970 Extreme3. I've had it for 1 year and never had any problems with it until now.