Did you ever find a solution to this? I'm suffering exactly the same problem. Can format the disk through windows, defrag it, error check it. Nothing causes any problems - but SonicStage (4.3) just refuses to stay connected. It will connect, disconnect, reconnect and so on. I've tried uninstalling / reinstalling sonicstage but not luck. Also doesn't appear to be a "real" connection fault as windows has no problems seeing it.