Open cmd ( if you have win 7 or 8 run as administrator )

Then set driver letter like this e: and hit enter ( don't know your letter for garmin device so you must change e to letter that your nuvi use )

then write this: chkdsk /f and hit enter and you will see if you have some error on device.

p.s.
You can also create backup of your nuvi and run prepusb to format your device and then add back your backup.

[Only registered and activated users can see links. ]