nuvi 1300 shuts off when SAVE is pressed

Hello all. first post here. Details:
Garmin nuvi 1300lmt
nuvi 1300 W KPI V4 LC 2GB
GPS version 4.30
software version 4.90
basemap: Worldwide Autoroute DEM NR 5.00

So here's the problem: I had the gps unit connected to my computer while I ran a defrag on the computer. the nuvi was unintentionally defragged in the process. In all aspects but one, the unit seems to operate normally. But one problem showed up: When I press SAVE to commit any map point to Favorites, the unit shuts off immediately.

My guess is that the defrag caused some folder or file to be sandwiched between others, and thus file or folder needs to grow to accomodate more favorites, so the unit gets confused and shuts down. This is only a guess.

What I have done: I tried cutting/pasting all non-map files from the nuvi to my computer and back again, recreating the folders on the nuvi manually before repasting the files back into the nuvi. I did this in the hope that the newly-created folders might be created in new addresses on the nuvi storage, but most of the folders were recreated right where they were when I cut them. So as of now, I still have a neatly defragged nuvi that navigates and operates perfectly EXCEPT for shutting down when I click to save favorites. Not a big deal but annoying.

The only files I never touched after the problem started were the map files. I'm starting to think that one or more of the map files are where new favorites are stored (I used to think favorites were all about .gpi and .gpx files, but I now think there's more to it than that).

Any help would be appreciated.