Ocaccionally I have that problem when I plug more than one USB device at at time.  I am sure you have already tried it but try unpluging all other usb devices such as cameras.  Reboot. Plug the device you want to read into "a different" usb port than you have tried.  Sometimes it works.  I still have problems with some devices.

 

Also you may try going to your virus program and clicking off the "personal firewall" while you try to read the device.