Please help!  I have 3 brand new Nano's.  The first time they're connected to my computer the music updates and they disconnect the way they're supposed to.  Unplug them and then try to update the music again and the iPod will not disconnect.  They are not being used as disks and if I try to disconnect them with the "Safely remove hardware" from my windows tray a pop up says "The device 'Generic volume' cannot be stopped right now.  Try stopping the device again later.'

Suggestions?