You're using an mp3 player right, not a USB jump drive?
I'm experimenting with my USB jump drive right now. I've been getting that same message randomly, but only with one of my jump drives. The other one (exact same stick) always works and I'm checking to see if it's because I "named" it in "My Computer"
So, I "named" the other one and I'm going to test and see if it still has any issues.
I'm not sure if you can do this same thing with mp3 players, but as far as I can tell, non-iPod mp3 players are just basically a USB jump drive with proprietary software/firmware included so that you can simply plug in some headphones and listen to music stored on it.
It's worth a shot
