Well Done Rosbif.
I was hoping that you would fix it.
I think that your original problem was that your nuvi drive was corrupt.
The Procedure for others (Nuvi 13xx and 14xx) should be something like this. (use Windows XP, not MAC)

1 Run GarminCure3 in Cure Mode to be able to access the internal drive.
2 Backup as many files as possible, not forgetting the hidden /.system folder to your PC.
3 Format the nuvi drive using [Only registered and activated users can see links. ] as a reference.
4 Run GarminCure3 in Original Mode.
5 The Nuvi Should now boot Run Webupdater.