If your USB 2.0 devices suddenly start acting weird and start to be detected as "unknown devices" or you receive "Your USB device has malfunctioned" error messages, try this simple fix:

      This is quite low-tech and I was skeptical until it fixed many previously unresolved issues that were not fixed with a BIOS upgrade, driver reinstalls/updates, MS hotfixes, reinstalling Windows, etc...

    1) Shutdown the PC

    2) Physically unplug the power cable from the PC/Wall

    3) Wait approx 30 minutes for residual power in power supply to dissipate (sometimes you can rush this by pressing the power button a few times after disconnecting the power)

    4) Plug the power back in and try your devices again

Like I said, this is low-tech, but it has worked numerous times for me. Hope you have luck with it too!