I've been having this problem on my G4, tiger 10.4.10. Sometimes I'll be dragging and dropping files (moving files around, back up, copying to usb drive or ipod, etc.) and sometimes it simply won't let me copy them over. For example right now i'm backing up a folder on my ipod. when I drag it from the hard disk to the pod it will not let me copy it over. Sometimes I'll try it a couple of days later and it'll work. I'm even making sure that none of the files are in use. It's even happened moving files on the same hd around. what gives?