There are picture galleries on a local newspaper's website that I can't view in Firefox with Adblock Plus enabled. (Disabling it, and refreshing the page, always fixes the problem).
So, guessing that it could be the same add-on that's causing your problem, I googled this line:
"adblock plus" "google maps"
Surprise, surprise, I found pages like this one (which appear to confirm my suspicion):
http://www.tysonkroeker.com/content/2014/06/03/google-maps-and-adblock-plus
So, if you've got Adblock Plus installed, try disabling it. You don't need to restart Firefox with extensions disabled. Simply go to 'Tools' (or click on the three line 'hamburger' icon at the top right) and then 'Add-ons'. If required, click on 'Extensions' and then on 'Disable' next to Adblock Plus. (It can be enabled again via the same route).