Después de buscar y buscar en español no encontré nada. Buscando en inglés hayé la solución:
1. Start Zune, then connect your phone to PC
2. Open Device Manager -> Portable Devices
3. Right click your device, then Uninstall
4. In Confirm Device Uninstall dialog select Delete the driver software for this device, then OK
5. Open Device Manager -> Windows Phone USB Devices
6. Right click Windows Phone USB, then Uninstall
7. In Confirm Device Uninstall dialog select Delete the driver software for this device, then OK
8. Reconnect your phone - Driver Software Installation dialog will appear and reinstall clean drivers.
9. Restart Zune to confirm there is no problem any more
Ahora va de maravilla.