You need to set the height and width for the GMaps container element to something sensible. Otherwise the map container will have 0 height, and thus seems “invisible”.
I got the maps in my theme working just fine be overriding the “max-width: 97.5%” for the img tags inside the Google Maps container element using “max-width: none”. This was ok, since I was using a child theme anyway, so I didn’t have to modify the original CSS files of Twenty Eleven.
Seems that the strange-looking “97.5%” rule is somehow related to the image auto-scaling feature of the WordPress themes, but I’m yet to find a good source explaining this (hack ?). Twenty Eleven theme developers: could you please explain this max-width thing in a couple of lines? What do I lose if I just disable this setting in my themes?
