Mel ... While your answer did not resolve the problem - I tried copying files one at a time with just a few files and had the same problem - after trying a few different things, re-reading your post made me think - maybe the USB HAS TO have the same name (I had given the new USB a different name than the one I was using) I reformatted the USB on the KORG using the same name as the first stick and VOILA !!! situation resolved ...
Thanks for responding, Mel ...