For me, with the same error, I had tried using a thumb drive that was formatted incorrectly. Once I formatted the thumb drive as Fat32, it worked great.
Formatting the USB thumb drive as Fat32 (instead of NTFS or exFat), solved the problem for me. Just right click on the drive in Windows and select the "Format" option and format as Fat32. Formatting will wipe out anything on the drive so you will have to copy the music onto the drive after doing the format.