My story in short:
Garmin Nuvi 3760 device. Reformatted, ran WebUpdater and installed all updates available. Then installed Europe NT 2013.3 map via MapSource.
Map shows in the list of maps (which is only this one) and I can search addresses, POIs etc. etc.
Problem: map is grey (in "View Map" mode AND while navigating). Only things I can see are pink route, POIs, starrt and finish points. That's it. No streets, buildings, landmark - nothing. Also tried to install the same map using MapInstall, made no difference. It makes my Garmin impossible to be used...
I DO NOT have a backup from when it was all OK.
Any ideas? Thanks in advance, great forum!
Thank you very much, problem solved by downloading Garmin Worldwide Autoroute DEM Basemap NR 5.01 and copying it to .System folder.