I would use JL AFTER you have backed it up. Then reload the OS.
If you have Vista, there are some issues with DM 4.7 . Seems that 4.7 and XP work very well. Either case, when my device got stuck, I disconnected it just for kicks and giggles then re-connected it. It seemed to pick-up where it left off. Mind you, I used loader.exe and not DM App installer.