I am Sonicstage 4.3 on Windows Vista and was experiencing the very same symptoms with my NW-HD5: The player was visible in windows, the remaining space on its disk even showed in Sonicstage, but going through the menus or anything else in Sonicstage was painfully slow. Then the transfer window would show the "Device not connected" message and start the connecting sequence over again. This then repeated a few times until eventually Sonicstage would stop working. Uninstalling/reinstalling Sonicstage, changing USB-cables, switching USB-ports... nothing would help. I noticed that my walkman was on drive L: on my system. In between C: and L: were a whole bunch of devices, among which a series of card readers. In system management I noticed these were also connected through the USB-controller. Since I don't use any of these, I disabled them in the device manager. After rebooting, my walkman now is connected as drive F: and now works fine with Sonicstage !!! I am completely godsmacked, but very, very relieved. Maybe my experience can point you in the direction of a solution?
