The fact is that multi-siteaccess with virtual host installation require multi API keys, one for each domain (http://admin., http://www., http://de., http://it., http://es., etc.) (well, at least for googlemap API).
In the PHP code and in tpl files, the ezini calls are written like this :
So after having generated your Gmap keys, you have to re-organize the original gis.ini like this :
* copy the original gis.ini in ../settings/override/
* rename the original ../extension/gis/settings/gis.ini in gis.ini.memo
* then create an empty gis.ini in each of your virtual hosted siteaccess
* in the ../settings/override/gis.ini, just comment the ApplicationID=XXX line
* copy the [Google] line and this ApplicationID= line in each of your siteaccess site.ini : in the ../settings/siteaccess/admin/gis.ini, in the ../settings/siteaccess/www/gis.ini, etc., then complete this line with the google map api key for your current virtual hosted siteaccess.