Ok, one of the two files should help. Don'd know which one as you didn't wrote your HwID:
For 827 is this one:
[Only registered and activated users can see links. ]
For 1091:
[Only registered and activated users can see links. ]
Instructions:
Copy one of the files (GUPDATE.GCD) on an SD to folder x:/Garmin/ and plug the SD card in the nuvi. Wait till the firmware flashes. Then you should have access to the memory and you could delete the problematic file (s).
If that is ok then you could flash with normal FW and everything whould be back to normal:
827:
[Only registered and activated users can see links. ]
1091:
[Only registered and activated users can see links. ]
Cheers,
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