"This item [-] cannot be copied because there is not enough free space" Help!

[Joelis]

Hello!

I'm trying to copy files across to an external flash drive (mp3 player), but a warning "This item [-] cannot be copied because there is not enough free space" keeps popping up, even though there is enough space!
I have deleted emptied the trash with the drive plugged in but to no avail!

Can anybody give me any help?
Thanks in advance

 

[Eidorian]

Are there any other files on the MP3 player? How big are the files that you're trying to move right now?

 

[Joelis]

There are other files on the player, yes. I'm trying to move across a 6mb song, and it says that there's 400-or-so mb free on the player itself.