OK I wiped it and created an empty Garmin folder. It did reboot OK. I cleared nonvol and got prompted for language settings when device restarted.

I then reconnected GE and reinstalled maps. No errors reported.

Device restarts and the same errors and behaviour as before

That is says no detail maps then cannot authenticate. Foursquare data visible but no maps as the old low detail map hasn't been copied back.

I'm wondering if the Garmin server is sending back an unlock file that for some reason wont work with my device.