Have you got v3.50 fw? It had shutdown issues. From the Garmin changelog:
Upgrade to current v3.90 if you have an earlier version but 1690 is region specific so make sure you use the correct region fw. See [Only registered and activated users can see links. ].Changes made from version 3.50 to 3.60:
Fixed issues that could potentially cause memory corruptions and unit shutdowns.