I suppose you haven't any backup of your nav.......
Have a look how to make a reset of your nuvi ...
Start with the unit OFF and unplugged from power
1. Touch and hold the lower right corner of the screen with an index finger or the eraser end of a pencil
2. Continue touching and holding the lower right hand corner of the screen then power the unit ON
3. Release the power button when the device powers ON. You will see a new message: Do you really want to erase all user data?
4. Remove your finger from the touchscreen when this message displays
5. Touch Yes
The device will automatically reset. Follow the on screen prompts then place your device in an area with a clear view of the sky until it acquires satellites.
Note: A master reset will erase all waypoints or favorites and will restore your unit to the default factory settings.
it's a try ,of course, if this not solve your problem, have a look [Only registered and activated users can see links. ]
Very strange that 1350 is detected.... did you see the internal content of the nav when you plug in the PC ? From My Computer ,enter the nuvi root and under the folder Garmin there is the GarminDevice.xml file : open with notepad or word editor and look the model it shows....
Have a nice day