Marble 1.2.0-1 is in extras-testing for some days now. If you're using it, please give it a vote: @Redsandro, Estel: Setting persistentTileCacheLimit=0 in the [Cache] section in /home/user/MyDocs/.config/kde.org/Marble Desktop Globe.conf disables cache deletion.
Setting Marble to offline mode should be a better workaround btw to avoid tile updates.
@Redsandro: To workaround the cache problem, edit openstreetmap.dgml and increase the cache timeout. It's currently one week.
I guess that the root of the problem was an Internet connection where you get some login screen.
For the search problem, can you check whether there's a .sqlite file for Berlin somewhere in /home/user/MyDocs/.local/share/marble/maps/earth/placemarks/?