title: Virtualbox: USB devices captured but not attached
body: <p>I'm using an Ubuntu 16.04 guest on Windows 10. 
  I have this strange problem: all USB devices are not attached even the ones that were working fine with a filter. 
  The devices are captured but not attached. If I try to click on a device under "Devices->USB->" I receive a message saying that the device is busy.</p>