If you brick your nuvi or you have loop on garmin logo screen here is the cure:
My nuvi 1300 was bricked and wont boot becouse folder text,voice,keyboard was corupt.
I change 0:/ in firmware to 1:/ (you dont need to calculate checksum if you replace 0 to 1).Then i copy folder text,voice,keyboard on SD card and flash nuvi with updater.exe.
Nuvi turn on.
I replace corrupted folder and turn nuvi of and flash with original firmware (not changed firmware) and now work perfect.
If you dont flash with original firmware after repaire you got only english text,keyboard and no sound,but after flash with original firmware your nuvi work like charm.