I tried the plugin with Twenty Ten, but the site will use the theme Bizco, from Themify.
In this theme the map loads, but no placemarks are shown. I checked in the Java Console what was the error, and it showed:
bgmp_createMarker(): Not all of the required data was passed in.
Any tip for a solution? My friend, who owns the site, does not want another theme! =(
Thanks a lot!
http://wordpress.org/extend/plugins/basic-google-maps-placemarks/