Try by holding the power button AFTER you've loaded the RGN cure file into Updater.exe. I think that the flash isn't being properly initiated before the device exits preboot, so keep the updater GUI visible with the RGN loaded with the radio button next to 'USB Device' enabled, connect USB and quickly press the device power button and keep holding it watching updater's GUI. IMMEDIATELY you see the device details in the window adjacent to 'USB Device' click OK button or just hit enter on your PC's keyboard. You may need to fluke the timing, so just keep trying the process over and over until you catch the right moment. Once the flash starts properly the device will hold in preboot until it finishes. If you have to do it again, force the device fully OFF by holding the power button down for between 10 and 30 seconds. If it can't be turned off in 30 seconds then you'll need to remove the battery each time.