I came across this at the weekend.
Trying to copy some files from a DVD to a flash drive and kept getting this error.
Tried everything - reformatted etc. but no joy.
So Mr. Google to the rescue.
One link suggested that the problem was that there is a limit to the number of files you can copy to the root directory of a USB drive.
Sounded suspect but made a folder under root and then copied the files to the folder.
Suddenly everything worked!