@Steflea Petru
If you are using SSL, you need to make sure all links are using HTTPS instead of HTTP, you need to do it also on plugin level.
If you go to file:
oc-content/plugins/google_maps/index.php
There are 2 occurences of HTTP:
http://maps.google.com/maps/api/js?sensor=false
http://maps.google.com/maps/geo?q=%s&output=json&sensor=false
should be replaced with:
https://maps.google.com/maps/api/js?sensor=false
https://maps.google.com/maps/geo?q=%s&output=json&sensor=false