You using OS 9 or 10? Sometimes, with 9, if file sharing is on, the computer will think that a disk is being shared so it won't let you eject it saying that it is in use. I don't know if this can happen with an ipod (I don't have one), but I think that it can. I don't know if it can happen under OS X. One way to fix it in to turn of file sharing. There should be other ways, but I don't know what they are.