Garmin Montana 650t GMA protection work around.

[itcheybum]

I don't know if anyone else has had the problem where you get the "unable to authenticate maps etc" message when loading but the latest Firmware update to 5.9 seems to have fixed the issue.
There seems to be a million work arounds with keygens and the like but this is by far the simplest way to do it:
GCD Update Procedure

Use the links in Firmware History to download the zipped file for the version you desire
Unzip the downloaded archive and extract the gcd file
Rename the gcd file to gupdate.gcd
Connect the Montana to your computer and enter USB Mass Storage Mode
Copy the gupdate.gcd file to [Montana]\Garmin\gupdate.gcd
Disconnect and reboot the Montana
Once the update is completed, the GPSr will delete the gupdate.gcd file
Credit to

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for the instructions

So far no other stability issues so only time will tell.