I successfully converted the 3790 to 3490 and used the device for almost a month. Today I wanted revert back to 3790 to take the device to the Garmin Service Center since I noticed some permanent spots on display.
I dragged and dropped the nuvi37xx_GCDFile__450.rgn file to the updater.exe and restarted the unit and pressed above G. It recognized the device and started the update. It gave me the message that it is successful and 0 second remaining but later some error message came, while it was restarting the device. I clicked ok and since than there is no logo and the device even doesn't connect to the PC.
I tried again and again restarting and pressing at the same area where G should appear, but nothing happens.
Now my device is like dead. When I restart, it just shows some background light thats all.