I tired to upload some new maps to my Garmin gps using MapSource (this is the default gps manager for Garmin products). I selected the maps in the MapSource software carefully to fit on the storage card of the gps. After about an hour waiting while it was calculated the map set the following message appeared: Ok, it seemd as a bug, so I tired to reduce the size of the map set, but it didn't help:
I decided to give an other chance: At this point a gave up.